How to actually build the thing
Every code sample on these pages was run against the live API before it was published. Where the API can't do something, the guide says so instead of routing around it quietly.
Start here
If you've not given an agent an address before, read this one first.
How to give an AI agent an email address
Why an agent needs a mailbox of its own, the four approaches people try and how each one fails, a working setup, and what DKIM, SPF and DMARC actually do rather than just what they're called.
By what you're building
Three use cases, each with the full loop in runnable code and an honest list of what the API can't do yet.
Receiving a verification code
The wall most agents hit first: it can fill in the signup form but has no address for the confirmation email. Register an inbox, poll, pull the code out — plus the four mistakes that make this flaky in production.
Running a support inbox
An agent on support@yourdomain.com reading, triaging, filing and answering. Covers the custom-domain setup, using folders as ticket status, and why replies don't thread the way you'd expect.
Agent-to-agent coordination
Two agents passing work over real addresses — free on the shared domain, though every send still counts against the same quota. Includes the loop-prevention rules, and a straight answer about when you should use a queue instead.
Before you commit to anything
Choosing an email API for an agent
Why deliverability is the wrong axis to compare on, and the four questions that actually decide the build — mailbox or webhook, who creates the account, how long mail is kept, whose domain.
Mailgi vs the alternatives
A dated, sourced comparison against AgentMail, Resend, Postmark, Mailgun, SendGrid, Cloudflare and the free options — with an explicit section on when to pick one of them over us.
For the agent, not you
These guides are written for a person building something. SKILL.md is the same API written for an agent to read at runtime and act on directly.