AI agents
Give an agent its own inbox on a handle you choose — send, receive, reply, read OTPs. Exposed as MCP tools for Claude Desktop & Cursor.
→ email for AI agents FREE EMAIL API · SEND + RECEIVE
The free email API that
The free email API that
sends and receives.
Most email APIs only send. Ollastack gives your code — and your AI agents — a real inbox over HTTP: send, receive replies, read verification codes, reply in-thread, and spin up disposable inboxes to test email in CI. One API, free to start, no credit card.
Free tier · send + receive + test inboxes · OpenAPI + MCP
/ send
Send an email in one call
Create a mailbox, send from its own identity. Plain HTTP — any language.
$ curl -X POST https://login.ollastack.com/api/mailboxes/{id}/send \ -H "Authorization: Bearer fmd_…" \ -H "Content-Type: application/json" \ -d '{"to":"user@example.com","subject":"Hi","text":"Hello from the API"}' { "id": "msg_…", "status": "sent" }
/ receive · the difference
Receive email — the part other APIs skip
Every mailbox has a real receiving address. Long-poll for the next message and read the bodies plus pre-extracted codes and links — no IMAP, no HTML scraping.
$ curl "https://login.ollastack.com/api/mailboxes/{id}/wait?timeout=60" \ -H "Authorization: Bearer fmd_…" { "from": "noreply@service.com", "subject": "Your verification code", "codes": ["920184"], # OTP, extracted for you "links": ["https://service.com/verify?token=…"] }
Then reply in-thread (POST …/messages/{id}/reply) — threading preserved. That's a real two-way conversation over an API.
/ what it's for
One API, three jobs
CI email testing
Disposable inboxes that let a test assert the welcome email, receipt, or reset link actually arrived — over HTTP, no mail server.
→ email testing APIApp email
Transactional send plus a real inbox for inbound — support replies, parsed inbound mail, two-way flows your app actually reads.
→ agent mail identity/ honest comparison
When to use this — and when not to
We're not a high-volume one-way blaster. We're the full-duplex one. Here's the honest split.
| Need | Ollastack | Send-only API (Resend/SendGrid/Mailgun) |
|---|---|---|
| Send transactional email | ✅ | ✅ |
| Receive email / real inbox | ✅ | — |
| Read OTP codes & links (extracted) | ✅ | — |
| Reply in-thread | ✅ | — |
| Disposable inboxes for CI testing | ✅ | — |
| MCP tools for AI agents | ✅ | — |
| High-volume one-way blasts | use a transactional sender | ✅ |
If you only need to send a lot of mail, a dedicated transactional provider is the right tool. If you need to receive, test, or hold two-way conversations — especially for AI agents — that's this.
/ faq
Free email API — common questions
Is there really a free email API?
Yes. The free tier gives you a real email API with no credit card — create mailboxes, send, receive, and read messages over HTTP, plus disposable test inboxes for CI. It's metered (a modest monthly send quota); for high-volume one-way blasts a dedicated transactional sender is a better fit, but for send-and-receive, agents, and testing the free tier covers real work.
Can the API receive email, not just send it?
Yes — that's the point. Most 'email APIs' only send. Ollastack gives each mailbox a real receiving address, so your app or agent can receive replies, read verification codes and links (pre-extracted), and reply in-thread — full-duplex over one API.
How is this different from Resend, SendGrid, or Mailgun?
Those are excellent one-way transactional senders. Ollastack is a full-duplex inbox API: send + receive + reply + test, built for two-way conversations and AI agents. For pure high-volume sending, use a transactional provider; for inboxes your code or agent operates, use this.
Can I use it for testing email in CI?
Yes. Create a disposable test inbox, point your app at its address, long-poll for the message, and assert on the extracted code or link — no mail server, same token. It's a drop-in for email-testing tools like Mailosaur.
Is it an email API for AI agents?
Yes. An agent can create a mailbox on a chosen handle, send from it, wait for replies, and read OTP codes — and the same endpoints are exposed as MCP tools so Claude Desktop or Cursor use them natively.
A free email API that actually receives.
Send, receive, reply, and test — one API, free to start, no credit card.
Get a free API key