Send email
AgentMail
Email API that gives AI agents their own inboxes to send, receive and thread messages, with webhooks and an MCP server.
Rate limits
- API rate limit
- Per organization; numbers not published; over the limit returns
429with aRetry-Afterheader3 - Emails per day
- Free 100, Developer 1,000, Startup 15,0003
- Emails per month
- Free 3,000, Developer 10,000, Startup no separate cap1
- Emails per month (other page)
- Free no monthly cap, Startup 150,0003
- Emails per 5 minutes
- Developer 100, Startup 1,500, Free no separate cap1
Other limits
- Storage
- Free 3 GB, Developer 10 GB, Startup unlimited1
- Request size
- Inline attachments: 6 MB per whole request9
- Agent sign-up before verification
- 1 inbox, no custom domains, 10 emails a day to the attached human only3
- Webhook delivery
- Endpoint must answer
2xxwithin 15 seconds; 8 attempts over about 27.5 hours10 - Inboxes and domains
- Free 3 inboxes, Developer 10 inboxes and 10 domains, Startup 150 and 1503
Read from AgentMail’s own pages on 2026-11-04. Every number links to the page a value came from. For agents, the same facts as markdown: /tools/send-email/agentmail.md