# Startup Mail

> Startup Mail is a focused custom-domain email service for small companies, software, and agents. It combines a human web inbox with forwarding, explicit team access, a REST API, TypeScript SDK, signed webhooks, and MCP.

## Instructions for AI agents

- Fetch any documentation page as clean Markdown by appending `.md` to its canonical URL.
- Send `Accept: text/markdown` to a documentation URL for the same Markdown representation.
- Use this file to discover pages, then fetch only the pages relevant to the task.
- Startup Mail permits direct conversations and requested transactional email; it does not permit newsletters, campaigns, or cold outreach.
- The public REST API base is `https://startupmail.dev/v1`; its OpenAPI specification is `https://startupmail.dev/openapi.json`.
- The Streamable HTTP MCP endpoint is `https://startupmail.dev/mcp`.

## Start here

- [Documentation](https://staging.startupmail.dev/docs.md): Set up a company inbox for people, products, and agents—without adopting the rest of an office suite.
- [Quickstart](https://staging.startupmail.dev/docs/quickstart.md): Go from a domain you own to a working two-way mailbox in about ten minutes.
- [How Startup Mail works](https://staging.startupmail.dev/docs/how-it-works.md): Understand the route from DNS to inbox, forwarding destination, webhook, API, or agent.

## Use Startup Mail

- [Domains and DNS](https://staging.startupmail.dev/docs/domains.md): Connect a domain, publish the four required record types, and diagnose verification.
- [Mailboxes](https://staging.startupmail.dev/docs/mailboxes.md): Create company addresses and choose who can read, send, and manage each one.
- [Use the web inbox](https://staging.startupmail.dev/docs/web-inbox.md): Read, search, organize, compose, and reply from Startup Mail’s focused mail surface.
- [Forward to Gmail or Outlook](https://staging.startupmail.dev/docs/forwarding.md): Receive company mail in an inbox you already use and reply through a protected relay.
- [Teams and private access](https://staging.startupmail.dev/docs/team-access.md): Invite people, assign workspace roles, and grant private mailbox access separately.
- [Send and reply](https://staging.startupmail.dev/docs/sending.md): Send expected email from the web inbox or developer interfaces and follow delivery state.
- [Receive mail and read threads](https://staging.startupmail.dev/docs/receiving.md): Work with incoming messages, labels, complete threads, and real-time notifications.
- [Attachments](https://staging.startupmail.dev/docs/attachments.md): Upload files before sending and download inbound files with mailbox authorization.

## Build with it

- [API overview](https://staging.startupmail.dev/docs/api-overview.md): Authenticate to the v1 REST API, choose capabilities, and handle responses and errors.
- [API reference](https://staging.startupmail.dev/docs/api-reference.md): The complete public endpoint surface for mailboxes, threads, messages, attachments, and webhooks.
- [TypeScript SDK](https://staging.startupmail.dev/docs/sdk.md): Use the typed Startup Mail client to work with mailboxes, threads, messages, files, and webhooks.
- [Webhooks](https://staging.startupmail.dev/docs/webhooks.md): Receive signed, retried HTTPS events when mail or domain state changes.
- [Agent inboxes](https://staging.startupmail.dev/docs/agent-inboxes.md): Provision isolated agent mailboxes, least-privilege keys, reviewed drafts, and communication guardrails.
- [MCP for agents](https://staging.startupmail.dev/docs/mcp.md): Give an agent narrowly scoped tools for listing, reading, sending, and replying to mailbox conversations.

## Operate safely

- [Usage and limits](https://staging.startupmail.dev/docs/usage-limits.md): Understand email events, storage, recipient and attachment limits, and workspace safety caps.
- [Security and privacy](https://staging.startupmail.dev/docs/security.md): How mailbox access, secret storage, HTML isolation, webhook signing, and delivery controls fit together.
- [Troubleshooting](https://staging.startupmail.dev/docs/troubleshooting.md): Resolve DNS, receiving, sending, forwarding, API, webhook, and access problems.

## Additional resources

- [Product website](https://staging.startupmail.dev/)
- [Acceptable use policy](https://staging.startupmail.dev/acceptable-use)
- [TypeScript SDK repository](https://github.com/gustavhartz/startupmail/tree/main/packages/sdk)
- [Source repository](https://github.com/gustavhartz/startupmail)
- [Full documentation bundle](https://staging.startupmail.dev/llms-full.txt)


## Comparisons

- [Compare email services by the job you need done](https://staging.startupmail.dev/compare.md): Compare Startup Mail with mailbox providers, email APIs, agent inbox platforms, and office suites without reducing the choice to a feature count.
- [Startup Mail vs AgentMail](https://staging.startupmail.dev/compare/agentmail-alternative.md): Compare Startup Mail and AgentMail for agent inboxes, company email, custom domains, APIs, webhooks, team access, and pricing.
- [Startup Mail vs Postmark](https://staging.startupmail.dev/compare/postmark-alternative.md): Compare Startup Mail and Postmark for transactional sending, inbound email, persistent inboxes, teams, APIs, analytics, and pricing.
- [Startup Mail vs Resend](https://staging.startupmail.dev/compare/resend-alternative.md): Compare Startup Mail and Resend for custom-domain email, inbound mail, APIs, MCP, human inboxes, transactional sending, and pricing.
- [Startup Mail vs Amazon SES](https://staging.startupmail.dev/compare/amazon-ses-alternative.md): Compare Startup Mail and Amazon SES for custom-domain email, sending, receiving, AWS setup, inboxes, APIs, scaling, and total cost.
- [Startup Mail vs Cloudflare Email Service](https://staging.startupmail.dev/compare/cloudflare-email-service-alternative.md): Compare Startup Mail and Cloudflare Email Service for custom-domain mail, Workers, agents, forwarding, persistent inboxes, APIs, SMTP, and pricing.
- [Startup Mail vs Google Workspace](https://staging.startupmail.dev/compare/google-workspace-alternative.md): Compare Startup Mail and Google Workspace for custom-domain email, shared inboxes, developer access, office apps, and per-user costs.

## Guides

- [How to get custom-domain email without an office suite](https://staging.startupmail.dev/guides/custom-domain-email-without-office-suite.md): Set up email on your own domain without buying calendars, documents, meetings, and other office-suite tools you may not need.
- [Email forwarding vs a real mailbox](https://staging.startupmail.dev/guides/email-forwarding-vs-real-mailbox.md): Learn when custom-domain email forwarding is enough, when you need a stored mailbox, and what happens when you reply from Gmail or Outlook.
- [Email aliases vs separate mailboxes vs shared inboxes](https://staging.startupmail.dev/guides/email-alias-vs-mailbox-vs-shared-inbox.md): Choose the right setup for founder@, hello@, and support@: an alias, a separate mailbox, or an inbox shared by a team.
- [The complete guide to email for AI agents](https://staging.startupmail.dev/guides/email-for-ai-agents.md): Learn how to give an AI agent a real mailbox with scoped access, durable threads, safe sending, webhooks, MCP tools, and human review.
- [How to secure an AI agent that reads email](https://staging.startupmail.dev/guides/secure-ai-agent-email.md): Build a safer email agent with a narrow threat model, mailbox-scoped access, recipient rules, stored drafts, human approval, and audit records.
- [Should an AI agent use Gmail or a dedicated mailbox?](https://staging.startupmail.dev/guides/ai-agent-gmail-vs-dedicated-mailbox.md): Choose between connecting an AI agent to Gmail and giving it a dedicated mailbox by comparing identity, OAuth access, isolation, human use, and cost.
- [How to give an AI agent an email address on your domain](https://staging.startupmail.dev/guides/give-ai-agent-email-address.md): Set up a custom-domain mailbox for an AI agent with safe DNS changes, narrow permissions, MCP or webhook access, and human approval.
- [Email API vs inbox API: What are you actually building?](https://staging.startupmail.dev/guides/email-api-vs-inbox-api.md): Learn the difference between a sending API, inbound email processing, and an inbox API, then choose the right email architecture for your product.
- [Transactional email service vs business email hosting](https://staging.startupmail.dev/guides/transactional-email-vs-business-email.md): Understand the difference between transactional email services and business email hosting, including inboxes, replies, pricing, and common use cases.
- [Inbound email webhook vs persistent mailbox: which do you need?](https://staging.startupmail.dev/guides/inbound-email-webhook-vs-persistent-mailbox.md): Compare inbound email webhooks with persistent mailboxes, including storage, threads, retries, human access, and the cases where you need both.