Guide, updated Oct 16, 2026
Best email APIs for AI agents
Inboxes and sending APIs for agents that talk over email. We list 3 email APIs. Summaries come from each vendor's own site and every link was checked on or before Oct 16, 2026.
Shortlist
All 3 at a glance
Alphabetical. Nothing in this guide is a paid placement.
| Tool | What it does | Open source | More |
|---|---|---|---|
| AgentMail | Email inbox API for agents: create, send, and receive real inboxes. | No | Alternatives |
| Mailgun | Email API to send, receive, and track email. | No | Alternatives |
| Resend | Developer email API for transactional and marketing mail. | No | Alternatives |
How to choose
What to check before you pick
- Direction: does the agent only send, or does it need a real inbox to receive and reply?
- Inbox creation: can you create inboxes on demand through the API?
- Deliverability: custom domains, SPF, DKIM and DMARC support.
- Webhooks for inbound mail and events.
- Pricing unit: per email or per inbox. Check each vendor's pricing page.
This checklist is general advice. Check each vendor's docs and pricing page for current details.
The tools
Each option in one paragraph
AgentMail
agentmail.toEmail inbox API for agents: create, send, and receive real inboxes.
In their words: “AgentMail | Email Inbox API for AI Agents”
Mailgun
mailgun.comEmail API to send, receive, and track email.
In their words: “Transactional Email API Service For Developers - Transactional Email API Service For Developers | Mailgun”
Resend
resend.comDeveloper email API for transactional and marketing mail.
In their words: “Resend · Email for developers”
Head to head
Compare them side by side
FAQ
Questions
Which email APIs does Agent Stack Directory list?
3: AgentMail, Mailgun, Resend.
Which of them are open source?
None of them is marked open source in our data.
How is this list ordered?
Alphabetically. No placement in this guide is paid. Sponsored and featured tools are labeled elsewhere on the site and never reordered here.
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