FREE EMAIL API · SEND + RECEIVE

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.

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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 endpoint

$ 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.

Then reply in-thread (POST …/messages/{id}/reply) — threading preserved. That's a real two-way conversation over an API.

curl endpoint

$ curl "https://login.ollastack.com/api/mailboxes/{id}/wait?timeout=60" \
    -H "Authorization: Bearer fmd_…"

{
  "from": "sender@domain.com",
  "subject": "Your verification code",
  "codes": ["920184"],          # OTP, extracted for you
  "links": ["https://service.com/verify?token=…"]
}

/ what it's for

One API, three jobs

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

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 API

App 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	✅

/ 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.