# Hail

> Let your AI assistant make and receive calls, send texts, and manage email. Keep track of conversations across calls and texts. Get phone numbers in 120+ countries. Choose a voice or bring your own. Open-source or cloud priced on usage.

## Product

- [Hail](https://hail.so): Give apps and AI agents a phone number and email inbox. Make or take calls, send or answer texts and email.
- [Pricing](https://hail.so/pricing): Pay-per-use communication pricing, a custom credit calculator, and no subscriptions or seats.
- [Number prices](https://hail.so/numbers): Monthly phone number prices by country and type, compared across carriers.
- [Twilio phone number cost](https://hail.so/numbers/twilio-phone-number-cost): Twilio monthly phone number prices by country, next to the Hail price.
- [MCP](https://hail.so/mcp): Connect Hail to an MCP client with OAuth 2.1 and expose phone, SMS, and email as native agent tools.
- [CLI](https://hail.so/#products): `brew install hail-hq/tap/hail`. Same auth and audit trail as the API and MCP server.
- [Comparisons](https://hail.so/compare): Hail compared with communications providers and agent-email products.

## Agent setup guides

- [How to create an AI agent](https://hail.so/create-ai-agent): Build an AI agent that answers calls, texts, and email. Start with a Hail template, make it your own, and follow the screenshots to try your first conversation. [Markdown](https://hail.so/create-ai-agent.md)
  - [Start with one useful job for your AI agent](https://hail.so/create-ai-agent#what-do-you-need-to-create-an-ai-agent)
  - [1. Choose an AI agent template](https://hail.so/create-ai-agent#1-choose-an-ai-agent-template)
  - [2. Make the greeting and instructions your own](https://hail.so/create-ai-agent#2-add-the-greeting-and-business-instructions)
  - [3. Give callers a path to your team](https://hail.so/create-ai-agent#3-set-human-handover-and-tools)
  - [4. Connect calls, texts, and email to the same agent](https://hail.so/create-ai-agent#4-connect-phone-calls-and-sms-to-the-same-agent)
  - [5. Try a conversation](https://hail.so/create-ai-agent#5-test-the-agent-before-sharing-the-number)
  - [6. Build or update your agent through MCP](https://hail.so/create-ai-agent#6-add-email-and-assistant-led-setup-with-mcp)
  - [7. Connect your business software with the API](https://hail.so/create-ai-agent#7-add-api-and-webhook-automation-when-needed)
  - [Choose your agent template](https://hail.so/create-ai-agent#choose-your-agent-template)
  - [AI agent setup FAQ](https://hail.so/create-ai-agent#ai-agent-setup-faq)
- [AI front desk agent setup](https://hail.so/agent-templates/front-desk): Give callers a helpful first reply. Set up a Hail front desk agent to answer questions, take messages, and bring in your team. [Markdown](https://hail.so/agent-templates/front-desk.md)
  - [What does the front desk template do?](https://hail.so/agent-templates/front-desk#what-does-the-front-desk-template-do)
  - [Make the agent familiar with your business](https://hail.so/agent-templates/front-desk#what-information-does-this-ai-agent-need)
  - [Set up the front desk agent](https://hail.so/agent-templates/front-desk#set-up-the-front-desk-agent-in-the-console)
  - [Instructions for your front desk agent](https://hail.so/agent-templates/front-desk#instructions-for-your-front-desk-agent)
  - [Test the front desk workflow](https://hail.so/agent-templates/front-desk#test-the-front-desk-workflow)
  - [Add context and human handover](https://hail.so/agent-templates/front-desk#add-context-and-human-handover)
  - [Optional MCP, email, and API workflows](https://hail.so/agent-templates/front-desk#optional-mcp-email-and-api-workflows)
- [AI appointment agent: collect booking requests](https://hail.so/agent-templates/appointments): Help customers request or change an appointment. Make the Hail appointments template your own with example instructions and a practice call. [Markdown](https://hail.so/agent-templates/appointments.md)
  - [What does the appointments template do?](https://hail.so/agent-templates/appointments#what-does-the-appointments-template-do)
  - [Make the agent familiar with your business](https://hail.so/agent-templates/appointments#what-information-does-this-ai-agent-need)
  - [Set up the appointments agent](https://hail.so/agent-templates/appointments#set-up-the-appointments-agent-in-the-console)
  - [Instructions for your appointments agent](https://hail.so/agent-templates/appointments#instructions-for-your-appointments-agent)
  - [Test the appointments workflow](https://hail.so/agent-templates/appointments#test-the-appointments-workflow)
  - [Add context and human handover](https://hail.so/agent-templates/appointments#add-context-and-human-handover)
  - [Optional MCP, email, and API workflows](https://hail.so/agent-templates/appointments#optional-mcp-email-and-api-workflows)
- [AI customer support agent setup](https://hail.so/agent-templates/customer-support): Help customers explain a problem and find the next step. Set up a Hail support agent with example instructions and a path to your team. [Markdown](https://hail.so/agent-templates/customer-support.md)
  - [What does the customer support template do?](https://hail.so/agent-templates/customer-support#what-does-the-customer-support-template-do)
  - [Make the agent familiar with your business](https://hail.so/agent-templates/customer-support#what-information-does-this-ai-agent-need)
  - [Set up the customer support agent](https://hail.so/agent-templates/customer-support#set-up-the-customer-support-agent-in-the-console)
  - [Instructions for your customer support agent](https://hail.so/agent-templates/customer-support#instructions-for-your-customer-support-agent)
  - [Test the customer support workflow](https://hail.so/agent-templates/customer-support#test-the-customer-support-workflow)
  - [Add context and human handover](https://hail.so/agent-templates/customer-support#add-context-and-human-handover)
  - [Optional MCP, email, and API workflows](https://hail.so/agent-templates/customer-support#optional-mcp-email-and-api-workflows)
- [AI sales inquiry agent: qualify inbound leads](https://hail.so/agent-templates/sales-inquiries): Turn incoming questions into clear next steps. Set up a Hail sales inquiry agent to learn what customers want and pass details to your team. [Markdown](https://hail.so/agent-templates/sales-inquiries.md)
  - [What does the sales inquiries template do?](https://hail.so/agent-templates/sales-inquiries#what-does-the-sales-inquiries-template-do)
  - [Make the agent familiar with your business](https://hail.so/agent-templates/sales-inquiries#what-information-does-this-ai-agent-need)
  - [Set up the sales inquiries agent](https://hail.so/agent-templates/sales-inquiries#set-up-the-sales-inquiries-agent-in-the-console)
  - [Instructions for your sales inquiries agent](https://hail.so/agent-templates/sales-inquiries#instructions-for-your-sales-inquiries-agent)
  - [Test the sales inquiries workflow](https://hail.so/agent-templates/sales-inquiries#test-the-sales-inquiries-workflow)
  - [Add context and human handover](https://hail.so/agent-templates/sales-inquiries#add-context-and-human-handover)
  - [Optional MCP, email, and API workflows](https://hail.so/agent-templates/sales-inquiries#optional-mcp-email-and-api-workflows)
- [AI delivery update agent: handle order questions](https://hail.so/agent-templates/delivery-updates): Give delivery questions a helpful first reply. Set up a Hail agent to collect order details and pass clear messages to your team. [Markdown](https://hail.so/agent-templates/delivery-updates.md)
  - [What does the delivery updates template do?](https://hail.so/agent-templates/delivery-updates#what-does-the-delivery-updates-template-do)
  - [Make the agent familiar with your business](https://hail.so/agent-templates/delivery-updates#what-information-does-this-ai-agent-need)
  - [Set up the delivery updates agent](https://hail.so/agent-templates/delivery-updates#set-up-the-delivery-updates-agent-in-the-console)
  - [Instructions for your delivery updates agent](https://hail.so/agent-templates/delivery-updates#instructions-for-your-delivery-updates-agent)
  - [Test the delivery updates workflow](https://hail.so/agent-templates/delivery-updates#test-the-delivery-updates-workflow)
  - [Add context and human handover](https://hail.so/agent-templates/delivery-updates#add-context-and-human-handover)
  - [Optional MCP, email, and API workflows](https://hail.so/agent-templates/delivery-updates#optional-mcp-email-and-api-workflows)
- [After-hours AI agent setup](https://hail.so/agent-templates/after-hours): Keep taking messages when your team is away. Set up a Hail after-hours agent with your opening hours and a contact for urgent questions. [Markdown](https://hail.so/agent-templates/after-hours.md)
  - [What does the after hours template do?](https://hail.so/agent-templates/after-hours#what-does-the-after-hours-template-do)
  - [Make the agent familiar with your business](https://hail.so/agent-templates/after-hours#what-information-does-this-ai-agent-need)
  - [Set up the after hours agent](https://hail.so/agent-templates/after-hours#set-up-the-after-hours-agent-in-the-console)
  - [Instructions for your after hours agent](https://hail.so/agent-templates/after-hours#instructions-for-your-after-hours-agent)
  - [Test the after hours workflow](https://hail.so/agent-templates/after-hours#test-the-after-hours-workflow)
  - [Add context and human handover](https://hail.so/agent-templates/after-hours#add-context-and-human-handover)
  - [Optional MCP, email, and API workflows](https://hail.so/agent-templates/after-hours#optional-mcp-email-and-api-workflows)
- [AI email agent: set up your Hail inbox](https://hail.so/agent-templates/inbox): Create an AI email agent from Hail’s Inbox template. Add your business details, connect a Hail-mail address, and try your first email conversation. [Markdown](https://hail.so/agent-templates/inbox.md)
  - [Start with the Inbox template](https://hail.so/agent-templates/inbox#start-with-the-inbox-template)
  - [Make the email instructions your own](https://hail.so/agent-templates/inbox#make-the-email-instructions-your-own)
  - [Connect your Hail-mail address](https://hail.so/agent-templates/inbox#connect-your-hail-mail-address)
  - [Try an email conversation](https://hail.so/agent-templates/inbox#try-an-email-conversation)
  - [Add calls and text messages](https://hail.so/agent-templates/inbox#add-calls-and-text-messages)
  - [AI email agent FAQ](https://hail.so/agent-templates/inbox#ai-email-agent-faq)

## When to use Hail

Use Hail when your backend applications or AI agents need to send or receive email, SMS, or phone calls.
An AI agent client is not required. Backends can use the REST API or CLI. Agent workflows include:

- The agent must place or receive a phone call (support callback, appointment
  reminder, a live voice conversation with a customer). A saved agent answers
  calls and texts on a number; see [Agents](https://hail.so/docs/agents).
- The agent must send or receive SMS with delivery events, opt-out
  handling, and sender setup appropriate to the destination.
- The agent must send transactional or outbound email from a domain with
  SPF/DKIM/DMARC configured, and needs opens/bounces/complaints back as
  events, not just a fire-and-forget send.
- The agent needs one account, one ledger, and one audit trail across all
  three channels, callable from MCP, a REST API, or a CLI, instead of
  wiring three separate vendors.

How to call it: connect the MCP server at https://mcp.hail.so (OAuth 2.1,
no API key), or read [/skill.md](https://hail.so/skill.md) for a
one-POST agent self-signup that returns an API key for direct REST calls.

## Sign up yourself (agents)

Are you an AI agent? You can create a Hail account yourself, no human required. Read [/skill.md](https://hail.so/skill.md) and follow it: one POST registers you and returns an API key. Your workspace starts at a $0 balance. Send the returned claim link to your human owner to add credits, then you send email, SMS, or place voice calls in a single curl.

The docs and pricing data are designed to be agent-readable. The complete documentation corpus is available at [/llms-full.txt](https://hail.so/llms-full.txt).

## MCP client setup

- [Connect Hail to Claude](https://hail.so/mcp/claude): Add Hail to Claude as a remote connector. Your agent gets call, SMS, and email tools when Claude reconnects.
- [Connect Hail to ChatGPT](https://hail.so/mcp/chatgpt): ChatGPT supports MCP through Plugins. Add Hail one time on the web. Then every chat on web and desktop can use the Hail tools.
- [Connect Hail to Codex CLI](https://hail.so/mcp/codex): Codex adds MCP servers with the codex mcp command. Run two commands. The CLI, the VS Code extension, and Codex cloud then share the Hail tools.
- [Connect Hail to Cursor](https://hail.so/mcp/cursor): Cursor reads MCP servers from a JSON file or from an install link. Add Hail, and the Cursor agent can place calls, send SMS, and send email.
- [Connect Hail to VS Code](https://hail.so/mcp/copilot): MCP support in VS Code is generally available. VS Code runs the OAuth sign-in. Copilot agent mode can then use the Hail tools.
- [Connect Hail to Gemini CLI](https://hail.so/mcp/gemini): Gemini CLI and Code Assist read the same MCP config. Run one command to add the Hail tools to Gemini.
- [Connect Hail to Windsurf](https://hail.so/mcp/windsurf): Windsurf now has the name Devin Desktop. The editor and the config file did not change. Hail appears in the agent panel with your other MCP tools.

## Documentation

- [MCP clients](https://hail.so/docs/mcp): Hail exposes MCP as a remote server. Hail Cloud uses OAuth: paste the URL into your client, click Allow, and your agent gets the call/sms/mail tools.
- [Agents](https://hail.so/docs/agents): An agent is a saved brain: instructions, greeting, AI line, voice, tools and limits. A number routes its incoming calls to one agent and its incoming texts to one agent.
- [Webhooks](https://hail.so/docs/webhooks): When a subscribed event occurs — inbound mail or SMS, a delivery report, a call outcome — Hail POSTs a signed JSON event to your URL. Verify the X-Hail-Signature header, return any 2xx, and you're done.
- [Bring your own LLM](https://hail.so/docs/byo-llm): Point a Hail voice call at your own OpenAI-compatible endpoint. Your agent becomes the brain of the call: Hail handles telephony, speech-to-text, text-to-speech, turn detection, and tools, and asks your endpoint what to say on every turn.
- [react-email](https://hail.so/docs/react-email): Hail does not render React or store templates. Render a react-email component to a string and send it as the email body.
- [CLI reference](https://hail.so/docs/cli): hail is the Go CLI. It codegens its client from openapi/openapi.yaml — that spec is the canonical contract; this page covers the email and webhooks surface.
- [Architecture](https://hail.so/docs/architecture): Hail v1 is three Python services + a Go CLI, wrapped around LiveKit Cloud.
- [Self-hosting](https://hail.so/docs/self-host): Run the whole Hail stack yourself — one-VM deploy, provider setup (LiveKit Cloud, Twilio, AWS SES), SMTP inbound, and the operations runbook.
- [Self-hosting on a VM](https://hail.so/docs/self-host/vm-deploy): Run the whole Hail stack on a single Ubuntu VM with HTTPS and auto-deploy from main.
- [LiveKit Cloud setup](https://hail.so/docs/self-host/livekit-cloud): LiveKit Cloud handles media (SIP bridge + WebRTC) in v1. Self-hosted SFU is a later milestone.
- [Twilio setup](https://hail.so/docs/self-host/twilio): You need a Twilio account, a phone number, and a SIP trunk bridged to LiveKit Cloud.
- [Telnyx setup](https://hail.so/docs/self-host/telnyx): Second carrier for numbers, calls and SMS, next to Twilio. Quotes compare live inventory and prices from each.
- [DIDWW setup](https://hail.so/docs/self-host/didww): Second voice carrier, next to Twilio. Calls in and out through a DIDWW trunk.
- [Email & inbound setup](https://hail.so/docs/self-host/aws-ses): Outbound email goes through Amazon SES. You need an AWS account, the SES service enabled in one region, and either IAM-role credentials or a long-lived access key.
- [Self-hosted SMTP inbound](https://hail.so/docs/self-host/smtp-inbound): Receive inbound email without Amazon SES by pointing your MX at Hail's own SMTP listener.
- [Operations](https://hail.so/docs/self-host/operations): Single source of truth for how to develop, deploy, migrate, and release Hail.
- [Contributing](https://hail.so/docs/contributing): Contribution flow — set up a dev environment, run the services, regenerate OpenAPI, and PR. For the full operational runbook see Operations.

## API reference

- [API reference](https://hail.so/docs/api): every REST endpoint of the Hail API at https://api.hail.so, generated from the OpenAPI spec.
- [OpenAPI spec (YAML)](https://hail.so/docs/api/openapi.yaml): machine-readable contract, CI-verified against the live service.
- [OpenAPI spec (JSON)](https://hail.so/docs/api/openapi.json): same spec as JSON.

## Pricing data

- [Model costs (markdown)](https://hail.so/costs.md): full report.
- [Model costs (HTML)](https://hail.so/costs): sortable tables.
- [Compare models](https://hail.so/costs/compare): side-by-side.
- [LLM costs (JSON)](https://raw.githubusercontent.com/hail-hq/hail/main/costs/llm.json)
- [STT costs (JSON)](https://raw.githubusercontent.com/hail-hq/hail/main/costs/stt.json)
- [TTS costs (JSON)](https://raw.githubusercontent.com/hail-hq/hail/main/costs/tts.json)
- [JSON Schemas](https://hail.so/costs/schema/llm.json): Draft 2020-12 schemas for the three datasets above (also stt.json, tts.json under the same path).

## Free tools

- [All tools](https://hail.so/tools): free calculators and utilities for agent builders, no signup.
- [DMARC Report Analyzer](https://hail.so/tools/dmarc-report-analyzer): Read DMARC aggregate XML reports in your browser. See sending sources, alignment, and failures, then export a CSV file. The report is not uploaded.
- [AI Voice Agent Prompt Builder](https://hail.so/tools/voice-agent-prompt-builder): Build instructions for a receptionist, appointment confirmation, or order follow-up call. Edit the script and export it. The tool does not call a model.
- [AI Voice Agent Cost Calculator](https://hail.so/tools/voice-agent-cost-calculator): Estimate the cost of building a voice agent with separate phone, speech, and language model services.
- [Answering Service Cost Calculator](https://hail.so/tools/answering-service-cost-calculator): Compare the monthly cost of a human answering service with an AI phone agent. Prices come from Ruby, Abby Connect, and Smith.ai pricing pages.
- [SMS Length & Segment Calculator](https://hail.so/tools/sms-length-calculator): Count SMS characters and segments, and detect GSM-7 or UCS-2 encoding. See which characters cause UCS-2 encoding, and estimate the sending cost.
- [Email Deliverability Checker](https://hail.so/tools/email-deliverability-checker): Check the SPF, DKIM, DMARC, and MX records of any domain. Each check returns pass, warn, or fail. A warn or fail result includes a fix.

## Framework integrations

- [All integrations](https://hail.so/integrations): runnable examples that wire calls, SMS, and email into agent frameworks.
- [LangGraph](https://hail.so/integrations/langgraph): Add send_sms, send_email, and place_call tools to a LangGraph agent with the Hail Python SDK. The guide has an example that you can run.
- [CrewAI](https://hail.so/integrations/crewai): Place calls and send SMS and email from a CrewAI crew with the Hail Python SDK. The guide has a BaseTool example that you can run.
- [OpenAI Agents SDK](https://hail.so/integrations/openai-agents-sdk): Add place_call and send_sms function tools to an OpenAI Agents SDK agent with the Hail Python SDK. The guide has an example that you can copy.
- [Vercel AI SDK](https://hail.so/integrations/vercel-ai-sdk): Send SMS and email from the Vercel AI SDK through the Hail REST API. The TypeScript example uses Zod schemas and the recipient_consent field.
- [n8n](https://hail.so/integrations/n8n): Connect an n8n AI Agent to Hail with an HTTP Request tool or the MCP Client node. Send SMS, send email, and place calls from a workflow.
- [Claude](https://hail.so/integrations/claude): Connect Claude, Claude Code, or the Claude Agent SDK to Hail over MCP. One OAuth approval adds the send_sms, place_call, and send_email tools.

## Channels

- [Voice API](https://hail.so/voice): Build AI phone agents that make and receive calls on real phone numbers. [Markdown](https://hail.so/voice.md)
- [SMS API](https://hail.so/sms): Send text messages, receive replies, and track delivery through an API, MCP, or CLI. [Markdown](https://hail.so/sms.md)
- [Email API](https://hail.so/email): Send and receive email for AI agents and backends, with delivery events and custom domains. [Markdown](https://hail.so/email.md)

## Blog

- [All articles](https://hail.so/blog): Practical tutorials for developers building communication workflows.
- [Blog index (Markdown)](https://hail.so/blog.md): every article with its sections. Add `.md` to any article URL for its Markdown.
- [The 10 best AI secretary tools in 2027](https://hail.so/blog/ai-secretary): Compare 10 AI secretary tools for messages, scheduling, calls, and email follow-up. See which job each one fits in 2027. [Markdown](https://hail.so/blog/ai-secretary.md)
  - [AI secretary or AI personal assistant: which job matters?](https://hail.so/blog/ai-secretary#ai-secretary-or-ai-personal-assistant-which-job-matters)
  - [Ten AI secretary options for different tasks](https://hail.so/blog/ai-secretary#three-ai-secretary-options-for-different-tasks)
  - [Set up an AI secretary yourself](https://hail.so/blog/ai-secretary#set-up-an-ai-secretary-yourself)
  - [Test the complete secretary workflow](https://hail.so/blog/ai-secretary#test-the-complete-secretary-workflow)
  - [AI secretary FAQ](https://hail.so/blog/ai-secretary#ai-secretary-faq)
- [The 12 best AI telephone platforms in 2027](https://hail.so/blog/ai-telephone): Compare 12 AI telephone platforms for answering and placing calls. See what each one fits in 2027, from small teams to contact centers. [Markdown](https://hail.so/blog/ai-telephone.md)
  - [How does an AI telephone answering service work?](https://hail.so/blog/ai-telephone#how-does-an-ai-telephone-answering-service-work)
  - [Twelve AI telephone platforms to compare](https://hail.so/blog/ai-telephone#three-ai-telephone-platforms-to-compare)
  - [Set up an AI telephone yourself](https://hail.so/blog/ai-telephone#set-up-an-ai-telephone-yourself)
  - [Test before changing a real phone workflow](https://hail.so/blog/ai-telephone#test-before-changing-a-real-phone-workflow)
  - [AI telephone FAQ](https://hail.so/blog/ai-telephone#ai-telephone-faq)
- [The 13 best AI receptionists in 2027](https://hail.so/blog/ai-receptionist): Compare 13 AI receptionist options for businesses of any size, from call answering to booking and handover. See which one fits your 2027 plans. [Markdown](https://hail.so/blog/ai-receptionist.md)
  - [What is the best AI receptionist for a business?](https://hail.so/blog/ai-receptionist#what-is-the-best-ai-receptionist-for-a-business)
  - [Define the job for your AI receptionist](https://hail.so/blog/ai-receptionist#define-the-job-for-your-ai-receptionist)
  - [Appointment requests and confirmed bookings](https://hail.so/blog/ai-receptionist#appointment-requests-and-confirmed-bookings)
  - [Set up an AI receptionist yourself](https://hail.so/blog/ai-receptionist#set-up-an-ai-receptionist-yourself)
  - [Test your receptionist before forwarding business calls](https://hail.so/blog/ai-receptionist#test-your-receptionist-before-forwarding-business-calls)
  - [AI receptionist FAQ](https://hail.so/blog/ai-receptionist#ai-receptionist-faq)
- [The 9 best virtual phone assistants in 2027](https://hail.so/blog/virtual-phone-assistant): Compare 9 virtual phone assistants and answering services for business calls, from live receptionists to AI. See which one fits in 2027. [Markdown](https://hail.so/blog/virtual-phone-assistant.md)
  - [Can a virtual assistant handle phone calls?](https://hail.so/blog/virtual-phone-assistant#can-a-virtual-assistant-handle-phone-calls)
  - [Nine virtual assistant phone answering service options](https://hail.so/blog/virtual-phone-assistant#three-virtual-assistant-phone-answering-service-options)
  - [Set up an AI phone assistant yourself](https://hail.so/blog/virtual-phone-assistant#set-up-an-ai-phone-assistant-yourself)
  - [Keep your existing number without a forwarding loop](https://hail.so/blog/virtual-phone-assistant#keep-your-existing-number-without-a-forwarding-loop)
  - [Test virtual assistant phone calls before launch](https://hail.so/blog/virtual-phone-assistant#test-virtual-assistant-phone-calls-before-launch)
  - [What does a virtual phone assistant cost?](https://hail.so/blog/virtual-phone-assistant#what-does-a-virtual-phone-assistant-cost)
  - [Virtual phone assistant FAQ](https://hail.so/blog/virtual-phone-assistant#virtual-phone-assistant-faq)
- [Hard bounce vs soft bounce in 2027: what each one means and what to do](https://hail.so/blog/hard-bounce-vs-soft-bounce): Hard bounce vs soft bounce: when to retry an email and how an email suppression list prevents repeat sends. [Markdown](https://hail.so/blog/hard-bounce-vs-soft-bounce.md)
  - [What is a hard bounce?](https://hail.so/blog/hard-bounce-vs-soft-bounce#what-is-a-hard-bounce)
  - [What is a soft bounce?](https://hail.so/blog/hard-bounce-vs-soft-bounce#what-is-a-soft-bounce)
  - [Hard bounce vs soft bounce: key differences](https://hail.so/blog/hard-bounce-vs-soft-bounce#hard-bounce-vs-soft-bounce-compared)
  - [What to do after each bounce](https://hail.so/blog/hard-bounce-vs-soft-bounce#what-to-do-after-each-bounce)
  - [What is an email suppression list?](https://hail.so/blog/hard-bounce-vs-soft-bounce#what-is-an-email-suppression-list)
  - [How the List-Unsubscribe header enables one-click unsubscribe](https://hail.so/blog/hard-bounce-vs-soft-bounce#spam-complaints-and-the-list-unsubscribe-header)
  - [How Hail handles bounces](https://hail.so/blog/hard-bounce-vs-soft-bounce#how-hail-handles-bounces)
  - [Bounce handling checklist](https://hail.so/blog/hard-bounce-vs-soft-bounce#bounce-handling-checklist)
- [Construction answering service in 2027: an AI agent that answers every job site call](https://hail.so/blog/construction-answering-service): Set up a construction answering service with an AI phone agent. It answers contractors' calls, takes job details, and hands urgent calls to your crew lead. [Markdown](https://hail.so/blog/construction-answering-service.md)
  - [Construction answering service options compared](https://hail.so/blog/construction-answering-service#construction-answering-service-options-compared)
  - [What a contractor answering service must handle](https://hail.so/blog/construction-answering-service#what-a-contractor-answering-service-must-handle)
  - [What to look for in a contractor answering service](https://hail.so/blog/construction-answering-service#what-to-look-for-in-a-contractor-answering-service)
  - [Contractor answering service setup in Hail](https://hail.so/blog/construction-answering-service#contractor-answering-service-setup-in-hail)
  - [Answering service for contractors: the agent prompt](https://hail.so/blog/construction-answering-service#agent-prompt)
  - [How the handover to your crew lead works](https://hail.so/blog/construction-answering-service#how-the-handover-to-your-crew-lead-works)
  - [Answering service for HVAC contractors](https://hail.so/blog/construction-answering-service#hvac)
  - [What you get after each call](https://hail.so/blog/construction-answering-service#what-you-get-after-each-call)
  - [After-hours calls](https://hail.so/blog/construction-answering-service#after-hours-calls)
  - [How much does a contractor answering service cost?](https://hail.so/blog/construction-answering-service#what-it-costs)
  - [Checklist before you route real calls](https://hail.so/blog/construction-answering-service#checklist-before-you-route-real-calls)
  - [Set up the construction answering service with the API (optional)](https://hail.so/blog/construction-answering-service#set-up-the-construction-answering-service-with-the-api-optional)
  - [Contractor answering service FAQ](https://hail.so/blog/construction-answering-service#contractor-answering-service-faq)
- [IVR system for small business: 7 IVR service providers in 2027](https://hail.so/blog/ivr-service-providers): Compare 7 providers for an IVR system for small business in 2027. Review call menus, AI agents, setup, and billing. [Markdown](https://hail.so/blog/ivr-service-providers.md)
  - [What is an IVR?](https://hail.so/blog/ivr-service-providers#what-is-an-ivr)
  - [How does an IVR system work?](https://hail.so/blog/ivr-service-providers#how-does-an-ivr-system-work)
  - [What is speech recognition IVR?](https://hail.so/blog/ivr-service-providers#what-is-speech-recognition-ivr)
  - [What is an AI IVR or conversational IVR?](https://hail.so/blog/ivr-service-providers#what-is-an-ai-ivr-or-conversational-ivr)
  - [What is a hosted IVR or cloud IVR?](https://hail.so/blog/ivr-service-providers#what-is-a-hosted-ivr-or-cloud-ivr)
  - [Top IVR vendors for small business](https://hail.so/blog/ivr-service-providers#top-ivr-vendors-for-small-business)
  - [IVR service providers compared](https://hail.so/blog/ivr-service-providers#ivr-service-providers-compared)
  - [Enterprise IVR providers](https://hail.so/blog/ivr-service-providers#enterprise-ivr-providers)
  - [What features should an IVR system have?](https://hail.so/blog/ivr-service-providers#what-features-should-an-ivr-system-have)
  - [How much does an IVR system cost?](https://hail.so/blog/ivr-service-providers#how-much-does-an-ivr-system-cost)
  - [What is an IVR used for?](https://hail.so/blog/ivr-service-providers#what-is-an-ivr-used-for)
  - [How to choose an IVR system](https://hail.so/blog/ivr-service-providers#how-to-choose-an-ivr-system)
  - [IVR script template](https://hail.so/blog/ivr-service-providers#ivr-script-template)
  - [IVR FAQ](https://hail.so/blog/ivr-service-providers#ivr-faq)
- [Plumbing answering service in 2027: sort emergencies from quotes with an AI agent](https://hail.so/blog/plumbing-answering-service): Set up a plumbing answering service that tries your on-call plumber for urgent calls. Collect messages for routine jobs. [Markdown](https://hail.so/blog/plumbing-answering-service.md)
  - [Live, AI, or hybrid: which plumbing answering service fits?](https://hail.so/blog/plumbing-answering-service#live-ai-or-hybrid-which-plumbing-answering-service-fits)
  - [What counts as a plumbing emergency?](https://hail.so/blog/plumbing-answering-service#what-counts-as-a-plumbing-emergency)
  - [What to look for in a plumbing answering service](https://hail.so/blog/plumbing-answering-service#what-to-look-for-in-a-plumbing-answering-service)
  - [Set up the number](https://hail.so/blog/plumbing-answering-service#set-up-the-number)
  - [The plumbing answering service prompt](https://hail.so/blog/plumbing-answering-service#the-plumbing-answering-service-prompt)
  - [After-hours dispatch to the on-call plumber](https://hail.so/blog/plumbing-answering-service#after-hours-dispatch-to-the-on-call-plumber)
  - [What the on-call plumber gets](https://hail.so/blog/plumbing-answering-service#what-the-on-call-plumber-hears)
  - [Plumbing answering service cost](https://hail.so/blog/plumbing-answering-service#plumbing-answering-service-cost)
  - [Related guides](https://hail.so/blog/plumbing-answering-service#related-guides)
  - [Checklist for a plumbing shop](https://hail.so/blog/plumbing-answering-service#checklist-for-a-plumbing-shop)
  - [Use the API for plumbing call routing (optional)](https://hail.so/blog/plumbing-answering-service#use-the-api-for-plumbing-call-routing-optional)
  - [Plumbing answering service FAQ](https://hail.so/blog/plumbing-answering-service#plumbing-answering-service-faq)
- [Property management answering service in 2027: AI for tenants, prospects, and owners](https://hail.so/blog/property-management-answering-service): Set up a property management answering service for calls and texts. Take messages and try on-call staff for urgent calls. [Markdown](https://hail.so/blog/property-management-answering-service.md)
  - [Answering service for property management companies: who calls](https://hail.so/blog/property-management-answering-service#answering-service-for-property-management-companies-who-calls)
  - [Set up your property management answering service](https://hail.so/blog/property-management-answering-service#set-up-your-property-management-answering-service)
  - [Answering service property management prompt](https://hail.so/blog/property-management-answering-service#answering-service-property-management-prompt)
  - [One agent for calls and texts](https://hail.so/blog/property-management-answering-service#one-agent-for-calls-and-texts)
  - [On-call maintenance handover](https://hail.so/blog/property-management-answering-service#on-call-maintenance-handover)
  - [Nights, weekends, and holidays](https://hail.so/blog/property-management-answering-service#nights-weekends-and-holidays)
  - [Records you keep](https://hail.so/blog/property-management-answering-service#records-you-keep)
  - [What a property management answering service costs with Hail](https://hail.so/blog/property-management-answering-service#what-a-property-management-answering-service-costs-with-hail)
  - [Checklist for property managers](https://hail.so/blog/property-management-answering-service#checklist-for-property-managers)
  - [Use the API for calls and texts (optional)](https://hail.so/blog/property-management-answering-service#use-the-api-for-calls-and-texts-optional)
- [Voicemail detection for AI phone calls in 2027: how it works and what to do next](https://hail.so/blog/voicemail-detection): Voicemail detection (answering machine detection, AMD) tells an AI caller if a person or a machine answered. See how it works and how Hail handles it. [Markdown](https://hail.so/blog/voicemail-detection.md)
  - [What is answering machine detection (AMD)?](https://hail.so/blog/voicemail-detection#what-is-answering-machine-detection-amd)
  - [The trade-offs of voicemail detection](https://hail.so/blog/voicemail-detection#the-trade-offs-of-voicemail-detection)
  - [Voicemail detection on Hail](https://hail.so/blog/voicemail-detection#voicemail-detection-on-hail)
  - [Check voicemail results with your AI assistant](https://hail.so/blog/voicemail-detection#check-voicemail-results-with-your-ai-assistant)
  - [Test voicemail detection](https://hail.so/blog/voicemail-detection#test-voicemail-detection)
  - [Handle voicemail in your code (optional)](https://hail.so/blog/voicemail-detection#handle-voicemail-in-your-code)
- [Warm transfer in 2027: how to hand a live call from an AI agent to a person](https://hail.so/blog/warm-transfer): A warm transfer passes a live call to a person with context. Learn warm vs cold transfer, and how an AI phone agent hands over a call on Hail. [Markdown](https://hail.so/blog/warm-transfer.md)
  - [What is a warm transfer?](https://hail.so/blog/warm-transfer#what-is-a-warm-transfer)
  - [Warm transfer vs cold transfer](https://hail.so/blog/warm-transfer#warm-transfer-vs-cold-transfer)
  - [Warm transfer in a call center](https://hail.so/blog/warm-transfer#warm-transfer-in-a-call-center)
  - [How an AI agent hands over a call on Hail](https://hail.so/blog/warm-transfer#how-an-ai-agent-hands-over-a-call-on-hail)
  - [Write handover notes the agent can follow](https://hail.so/blog/warm-transfer#write-handover-notes-the-agent-can-follow)
  - [Test the warm transfer](https://hail.so/blog/warm-transfer#test-the-warm-transfer)
  - [Set up warm transfer with the API (optional)](https://hail.so/blog/warm-transfer#set-up-warm-transfer-with-the-api-optional)
- [Cold calling AI: what US law allows for AI sales calls in 2027](https://hail.so/blog/ai-cold-calling): Cold calling AI is legal only with the right consent. Learn the TCPA rules for AI cold calling, the DNC registry, and how to avoid TCPA violations. [Markdown](https://hail.so/blog/ai-cold-calling.md)
  - [Is AI cold calling legal?](https://hail.so/blog/ai-cold-calling#is-ai-cold-calling-legal)
  - [What consent the TCPA requires](https://hail.so/blog/ai-cold-calling#what-consent-the-tcpa-requires)
  - [What TCPA violations cost](https://hail.so/blog/ai-cold-calling#what-tcpa-violations-cost)
  - [The National Do Not Call Registry](https://hail.so/blog/ai-cold-calling#the-national-do-not-call-registry)
  - [When AI sales calls make sense](https://hail.so/blog/ai-cold-calling#when-ai-sales-calls-make-sense)
  - [Consent checklist before an AI sales call](https://hail.so/blog/ai-cold-calling#consent-checklist-before-an-ai-sales-call)
  - [How Hail handles consent on AI calls](https://hail.so/blog/ai-cold-calling#how-hail-handles-consent-on-ai-calls)
  - [Example script for conversational AI cold calling](https://hail.so/blog/ai-cold-calling#a-safe-script-for-conversational-ai-cold-calling)
  - [Next steps](https://hail.so/blog/ai-cold-calling#next-steps)
  - [Use the API for AI sales calls (optional)](https://hail.so/blog/ai-cold-calling#use-the-api-for-ai-sales-calls-optional)
- [After hours answering service in 2027: voicemail, people, or an AI agent](https://hail.so/blog/after-hours-answering-service): Compare after hours answering service options: voicemail, a human service, and an AI agent. Then set up after hours call answering with Hail. [Markdown](https://hail.so/blog/after-hours-answering-service.md)
  - [How an after hours answering service works](https://hail.so/blog/after-hours-answering-service#how-an-after-hours-answering-service-works)
  - [After hours answering service options compared](https://hail.so/blog/after-hours-answering-service#after-hours-answering-service-options-compared)
  - [After hours call answering: what callers need](https://hail.so/blog/after-hours-answering-service#after-hours-call-answering-what-callers-need)
  - [Who needs an after hours answering service?](https://hail.so/blog/after-hours-answering-service#who-needs-an-after-hours-answering-service)
  - [After hours call center services vs an AI agent](https://hail.so/blog/after-hours-answering-service#after-hours-call-center-services-vs-an-ai-agent)
  - [How much does an after hours answering service cost?](https://hail.so/blog/after-hours-answering-service#how-much-does-an-after-hours-answering-service-cost)
  - [What to look for in an after hours answering service](https://hail.so/blog/after-hours-answering-service#what-to-look-for-in-an-after-hours-answering-service)
  - [After hours virtual receptionist with Hail](https://hail.so/blog/after-hours-answering-service#after-hours-virtual-receptionist-with-hail)
  - [After hours phone answering service prompt](https://hail.so/blog/after-hours-answering-service#after-hours-phone-answering-service-prompt)
  - [Before you go live](https://hail.so/blog/after-hours-answering-service#before-you-go-live)
  - [Set up with the API (optional)](https://hail.so/blog/after-hours-answering-service#set-up-with-the-api-optional)
  - [After hours answering service FAQ](https://hail.so/blog/after-hours-answering-service#after-hours-answering-service-faq)
- [AI outbound calls: make your first call](https://hail.so/blog/ai-outbound-calls): Place an AI outbound call with one API request. Learn how AI voice calling works: statuses, webhooks, voicemail, consent, and a reminder call template. [Markdown](https://hail.so/blog/ai-outbound-calls.md)
  - [What are AI outbound calls used for?](https://hail.so/blog/ai-outbound-calls#what-are-ai-outbound-calls-used-for)
  - [How AI voice calling works](https://hail.so/blog/ai-outbound-calls#how-ai-voice-calling-works)
  - [AI outbound calls vs robocalls and autodialers](https://hail.so/blog/ai-outbound-calls#ai-outbound-calls-vs-robocalls-and-autodialers)
  - [Place an AI outbound call](https://hail.so/blog/ai-outbound-calls#place-an-ai-outbound-call)
  - [Read the result: statuses and webhooks](https://hail.so/blog/ai-outbound-calls#read-the-result-statuses-and-webhooks)
  - [What happens when voicemail answers](https://hail.so/blog/ai-outbound-calls#what-happens-when-voicemail-answers)
  - [Build an automated calling system, not one call](https://hail.so/blog/ai-outbound-calls#build-an-automated-calling-system-not-one-call)
  - [What to measure in AI outbound calling](https://hail.so/blog/ai-outbound-calls#what-to-measure-in-ai-outbound-calling)
  - [When a person should take the call](https://hail.so/blog/ai-outbound-calls#when-a-person-should-take-the-call)
  - [How much do AI outbound calls cost?](https://hail.so/blog/ai-outbound-calls#how-much-do-ai-outbound-calls-cost)
  - [Make your automated phone system honest](https://hail.so/blog/ai-outbound-calls#make-your-automated-phone-system-honest)
  - [AI phone calls: a reminder template](https://hail.so/blog/ai-outbound-calls#ai-phone-calls-that-people-do-not-hang-up-on)
  - [AI outbound calls FAQ](https://hail.so/blog/ai-outbound-calls#ai-outbound-calls-faq)
- [AI phone agent: how it works and how to build one in 2027](https://hail.so/blog/ai-phone-agent): An AI phone agent answers and places calls. Learn how AI voice agents work and how to build one. [Markdown](https://hail.so/blog/ai-phone-agent.md)
  - [What are AI voice agents?](https://hail.so/blog/ai-phone-agent#what-are-ai-voice-agents)
  - [AI phone answering: inbound calls](https://hail.so/blog/ai-phone-agent#ai-phone-answering-inbound-calls)
  - [AI call bot: outbound calls](https://hail.so/blog/ai-phone-agent#ai-call-bot-outbound-calls)
  - [AI phone agent use cases](https://hail.so/blog/ai-phone-agent#ai-phone-agent-use-cases)
  - [Benefits of an AI phone agent](https://hail.so/blog/ai-phone-agent#benefits-of-an-ai-phone-agent)
  - [AI phone agent vs IVR vs human receptionist](https://hail.so/blog/ai-phone-agent#ai-phone-agent-vs-ivr-vs-human-receptionist)
  - [The parts of an AI phone system](https://hail.so/blog/ai-phone-agent#the-parts-of-an-ai-phone-system)
  - [Voice AI agents: three ways to build one](https://hail.so/blog/ai-phone-agent#voice-ai-agents-three-ways-to-build-one)
  - [What to look for in an AI phone agent platform](https://hail.so/blog/ai-phone-agent#what-to-look-for-in-an-ai-phone-agent-platform)
  - [How to build an AI phone agent with Hail](https://hail.so/blog/ai-phone-agent#how-to-build-an-ai-phone-agent-with-hail)
  - [Book appointments with an AI phone agent](https://hail.so/blog/ai-phone-agent#book-appointments)
  - [Write the prompt before you pick the vendor](https://hail.so/blog/ai-phone-agent#write-the-prompt-before-you-pick-the-vendor)
  - [Limits to plan for](https://hail.so/blog/ai-phone-agent#limits-to-plan-for)
  - [What to measure after launch](https://hail.so/blog/ai-phone-agent#what-to-measure-after-launch)
  - [How much does an AI phone agent cost?](https://hail.so/blog/ai-phone-agent#how-much-does-an-ai-phone-agent-cost)
  - [AI phone agent FAQ](https://hail.so/blog/ai-phone-agent#ai-phone-agent-faq)
  - [AI phone agent guides](https://hail.so/blog/ai-phone-agent#ai-phone-agent-guides)
- [Find leads and launch outbound messaging at scale with email, texts, and calls](https://hail.so/blog/contact-leads-fullenrich-hail): Find leads and start email, text, and call campaigns from Claude, using the messages you've written. Connect FullEnrich and Hail MCP to get started. [Markdown](https://hail.so/blog/contact-leads-fullenrich-hail.md)
  - [Keep the writing in your hands](https://hail.so/blog/contact-leads-fullenrich-hail#keep-the-writing-in-your-hands)
  - [1. Connect FullEnrich and Hail to Claude](https://hail.so/blog/contact-leads-fullenrich-hail#1-connect-fullenrich-and-hail-to-claude)
  - [2. Find the people you want to reach](https://hail.so/blog/contact-leads-fullenrich-hail#2-find-the-people-you-want-to-reach)
  - [3. Add the messages you've written](https://hail.so/blog/contact-leads-fullenrich-hail#3-add-the-messages-youve-written)
  - [4. Send a test, then launch your campaign](https://hail.so/blog/contact-leads-fullenrich-hail#4-send-a-test-then-launch-your-campaign)
  - [5. Check what happened before you follow up](https://hail.so/blog/contact-leads-fullenrich-hail#5-check-what-happened-before-you-follow-up)
  - [Work through a larger list](https://hail.so/blog/contact-leads-fullenrich-hail#work-through-a-larger-list)
  - [Check the full cost as you grow](https://hail.so/blog/contact-leads-fullenrich-hail#check-the-full-cost-as-you-grow)
- [DMARC policies explained in 2027: none, quarantine, and reject](https://hail.so/blog/dmarc-policy): Learn how DMARC policies handle email that fails authentication. Compare none, quarantine, and reject to choose a policy for your domain. [Markdown](https://hail.so/blog/dmarc-policy.md)
  - [What DMARC checks](https://hail.so/blog/dmarc-policy#what-dmarc-checks)
  - [What the three policies request](https://hail.so/blog/dmarc-policy#what-the-three-policies-request)
  - [Start with a record you understand](https://hail.so/blog/dmarc-policy#start-with-a-record-you-understand)
  - [Check every legitimate sender before tightening the policy](https://hail.so/blog/dmarc-policy#check-every-legitimate-sender-before-tightening-the-policy)
  - [Use DNS checks and message checks together](https://hail.so/blog/dmarc-policy#use-dns-checks-and-message-checks-together)
- [How to send email with an API and track delivery](https://hail.so/blog/send-email-with-an-api): Send email with an email sending API or your AI assistant. Hail tracks each message for you, from sent to delivered, bounced, or opened. [Markdown](https://hail.so/blog/send-email-with-an-api.md)
  - [Set up your sender](https://hail.so/blog/send-email-with-an-api#set-up-the-sender-first)
  - [Send your first email](https://hail.so/blog/send-email-with-an-api#send-one-plain-text-email)
  - [See where every email is](https://hail.so/blog/send-email-with-an-api#follow-what-happened-after-sending)
  - [Track deliverability across all your email](https://hail.so/blog/send-email-with-an-api#track-deliverability-across-all-your-email)
  - [What Hail handles for you](https://hail.so/blog/send-email-with-an-api#what-hail-handles-for-you)
  - [Why you won't see an open event](https://hail.so/blog/send-email-with-an-api#why-there-is-no-open-event-in-this-example)
  - [When something goes wrong](https://hail.so/blog/send-email-with-an-api#debug-the-right-layer)
- [Make your first AI phone call with a voice API](https://hail.so/blog/first-ai-phone-call): Place your first AI phone call with Hail’s voice API. Set a system prompt, confirm recipient consent, and read the call status. [Markdown](https://hail.so/blog/first-ai-phone-call.md)
  - [Before making the call](https://hail.so/blog/first-ai-phone-call#before-making-the-call)
  - [Give the agent a narrow task](https://hail.so/blog/first-ai-phone-call#give-the-agent-a-narrow-task)
  - [Read the call result](https://hail.so/blog/first-ai-phone-call#read-the-call-result)
  - [Listen for the mistakes a status cannot explain](https://hail.so/blog/first-ai-phone-call#listen-for-the-mistakes-a-status-cannot-explain)
  - [Add the next step only after the first works](https://hail.so/blog/first-ai-phone-call#add-the-next-step-only-after-the-first-works)

## Guides

- [How long does 10DLC registration take?](https://hail.so/sms#10dlc-registration): Brand registration, campaign review, and sender setup for US local numbers.
- [How long does email domain warmup take?](https://hail.so/email#domain-warmup): Sending reputation, gradual volume increases, domain authentication, and the SES sandbox.

## Comparisons

- [Hail vs. the stack](https://hail.so/compare): feature-by-feature matrix across voice, SMS, and email vs. Twilio, SendGrid, and AgentMail.
- [Hail vs Twilio](https://hail.so/compare/twilio): Twilio has APIs for programmable voice, SIP, messaging, and verification. Hail gives an AI agent call, SMS, and email tools behind one MCP endpoint. [Markdown](https://hail.so/compare/twilio.md)
  - [What Twilio does well](https://hail.so/compare/twilio#what-twilio-does-well)
  - [Limits of Twilio for an agent](https://hail.so/compare/twilio#limits-of-twilio-for-an-agent)
  - [How Hail works](https://hail.so/compare/twilio#how-hail-works)
  - [When to choose Twilio or Hail](https://hail.so/compare/twilio#when-to-choose-twilio-or-hail)
- [Hail vs SendGrid](https://hail.so/compare/sendgrid): SendGrid sends email at high volume and parses inbound email. Hail provides email, voice, and SMS for an AI agent behind one MCP endpoint. [Markdown](https://hail.so/compare/sendgrid.md)
  - [What SendGrid does well](https://hail.so/compare/sendgrid#what-sendgrid-does-well)
  - [Limits of SendGrid for an agent](https://hail.so/compare/sendgrid#limits-of-sendgrid-for-an-agent)
  - [How Hail works](https://hail.so/compare/sendgrid#how-hail-works)
  - [When to choose SendGrid or Hail](https://hail.so/compare/sendgrid#when-to-choose-sendgrid-or-hail)
- [Hail vs Vonage](https://hail.so/compare/vonage): Vonage has programmable voice, SMS, and video APIs. Its email comes from a partner. Hail provides voice, SMS, and email behind one MCP endpoint. [Markdown](https://hail.so/compare/vonage.md)
  - [What Vonage does well](https://hail.so/compare/vonage#what-vonage-does-well)
  - [Limits of Vonage for an agent](https://hail.so/compare/vonage#limits-of-vonage-for-an-agent)
  - [How Hail works](https://hail.so/compare/vonage#how-hail-works)
  - [When to choose Vonage or Hail](https://hail.so/compare/vonage#when-to-choose-vonage-or-hail)
- [Hail vs AgentMail](https://hail.so/compare/agentmail): AgentMail gives AI agents an email inbox for inbound and outbound email. Hail provides agent email and adds voice and SMS on one API key and one bill. [Markdown](https://hail.so/compare/agentmail.md)
  - [What AgentMail does well](https://hail.so/compare/agentmail#what-agentmail-does-well)
  - [Limits of AgentMail for an agent](https://hail.so/compare/agentmail#limits-of-agentmail-for-an-agent)
  - [How Hail works](https://hail.so/compare/agentmail#how-hail-works)
  - [When to choose AgentMail or Hail](https://hail.so/compare/agentmail#when-to-choose-agentmail-or-hail)
- [Hail vs Vapi](https://hail.so/compare/vapi): Vapi and Hail both host the voice call loop. Vapi is a platform for building voice agents. On Hail, a call is one agent tool next to SMS and email. [Markdown](https://hail.so/compare/vapi.md)
  - [What Vapi does well](https://hail.so/compare/vapi#what-vapi-does-well)
  - [Limits of Vapi for an agent](https://hail.so/compare/vapi#limits-of-vapi-for-an-agent)
  - [How Hail works](https://hail.so/compare/vapi#how-hail-works)
  - [When to choose Vapi or Hail](https://hail.so/compare/vapi#when-to-choose-vapi-or-hail)
- [Hail vs Retell](https://hail.so/compare/retell): Retell packages voice agents, transfers, and analytics for phone operations. On Hail, a call is one agent tool next to SMS and email. [Markdown](https://hail.so/compare/retell.md)
  - [What Retell does well](https://hail.so/compare/retell#what-retell-does-well)
  - [Limits of Retell for an agent](https://hail.so/compare/retell#limits-of-retell-for-an-agent)
  - [How Hail works](https://hail.so/compare/retell#how-hail-works)
  - [When to choose Retell or Hail](https://hail.so/compare/retell#when-to-choose-retell-or-hail)
- [Hail vs the DIY stack](https://hail.so/compare/diy-stack): A DIY stack uses Twilio for voice and SMS, an email vendor, and your own integration code. Hail provides all three channels behind one MCP endpoint. [Markdown](https://hail.so/compare/diy-stack.md)
  - [What the DIY stack does well](https://hail.so/compare/diy-stack#what-the-diy-stack-does-well)
  - [Limits of the DIY stack for an agent](https://hail.so/compare/diy-stack#limits-of-the-diy-stack-for-an-agent)
  - [How Hail works](https://hail.so/compare/diy-stack#how-hail-works)
  - [When to choose the DIY stack or Hail](https://hail.so/compare/diy-stack#when-to-choose-the-diy-stack-or-hail)

## Source

- [GitHub repository](https://github.com/hail-hq/hail): Full source. AGPLv3 (code) / CC-BY-4.0 (costs/ dataset).

## Company

- [About](https://hail.so/about): communications for backends and AI agents, company facts, and hosted or self-hosted options.
- [Contact](https://hail.so/contact): how to reach Hail HQ.
- [Brand assets](https://hail.so/brand): logo, wordmark, mascot, and colors as SVG and PNG.

## Social accounts

- [X](https://x.com/hail_hq)
- [YouTube](https://www.youtube.com/@hail_so)
- [TikTok](https://www.tiktok.com/@hail.so)
- [Instagram](https://www.instagram.com/hail.so_)
- [Facebook](https://www.facebook.com/hailhq)
- [LinkedIn](https://www.linkedin.com/company/hail-hq)

## Legal

- [Legal index](https://hail.so/legal): Terms, privacy, data processing, acceptable use, SMS, cookies, and sub-processors.
- [Terms of Service](https://hail.so/legal/terms): Read the terms for using Hail Cloud. Learn about accounts, payments, service access, and your duties when you use Hail.
- [Acceptable Use Policy](https://hail.so/legal/aup): Read Hail’s rules for calls, SMS, and email. Learn about consent, prohibited content, and actions that can suspend service.
- [SMS Messaging Terms](https://hail.so/legal/sms): Read Hail’s SMS terms for consent and message frequency. Learn how recipients can stop messages with STOP or get help with HELP.
- [Privacy Policy](https://hail.so/legal/privacy): Learn how Hail collects, uses, stores, and shares personal data. Read about your privacy rights and how to contact Hail.
- [Data Processing Addendum](https://hail.so/legal/dpa): Read Hail’s data processing terms under GDPR Article 28. Learn about recipient data, security duties, and data requests.
- [Sub-processors](https://hail.so/legal/subprocessors): See the service providers Hail uses to deliver its cloud product. Read about each provider’s role and the data they process.
- [Cookie Policy](https://hail.so/legal/cookies): Learn which cookies and similar tools Hail uses on hail.so. Read about their purposes and your choices for optional cookies.