A free API to send email in one call
Send email with one HTTP POST — no SMTP, no mail server. A free API to send email, the deliverability basics, and how to receive the reply too.
The fastest way to send an email from code isn’t SMTP — it’s one HTTP call. No mail server, no host/port/password, no library quirks. Here’s a free API to send email in a single POST, plus the deliverability basics and the honest limits.
The one call
Create a mailbox once, then send from it. That’s it:
curl -X POST https://login.ollastack.com/api/mailboxes/mbx_.../send \
-H "Authorization: Bearer $TOKEN" \
-H "Content-Type: application/json" \
-d '{
"to": "user@example.com",
"subject": "Hello",
"text": "Sent with a single API call — no SMTP."
}'
# → { "id": "msg_…", "status": "sent" }
No smtp.host, no port 587, no app password. An API token and one HTTPS request.
No SMTP to set up
SMTP makes you configure a host, a port, TLS, and credentials, then handle connection errors and timeouts. An HTTP send API removes all of it — the call either returns a message id or a clear error you can act on. That’s the whole appeal: send mail without operating mail infrastructure.
Deliverability basics
One call still has to reach the inbox:
- Out of the box, mail sends from the platform’s verified domain with SPF/DKIM/DMARC already passing.
- To send from your domain, add a custom sender domain and publish the DNS records — see DKIM, SPF & DMARC. Until verified, delivery falls back to the authenticated platform sender, so a DNS mistake degrades branding, never delivery.
The honest limit
The free send quota is modest and monthly — perfect for transactional sends, agent mail, and testing, not for bulk marketing. For high-volume blasts, use a dedicated transactional provider; for send plus receive on a free tier, this is the simpler path.
Bonus: receive the reply
Because each mailbox also receives, the same token can long-poll for the response — something most send-only APIs can’t do:
curl "https://login.ollastack.com/api/mailboxes/mbx_.../wait?timeout=60" \
-H "Authorization: Bearer $TOKEN"
See the email API overview and the free email API service guide for the full picture.
Send your first email free — one call, no SMTP, no credit card.
Frequently asked questions
What's the simplest free API to send email?
A single authenticated HTTP POST: create a mailbox once, then POST to /api/mailboxes/{id}/send with to, subject, and text or html. No SMTP server, no credentials beyond an API token, and the free tier needs no credit card.
Do I need SMTP or a mail server?
No. The API handles delivery — you make one HTTPS call. There's no SMTP host, port, or password to configure, and nothing to run.
Will the email land in the inbox?
Mail sent from the platform's verified domain is authenticated (SPF/DKIM/DMARC) out of the box. To send from your own domain, add a custom sender domain and publish the DNS records; until then it falls back to the authenticated platform sender.
Can the same API also receive replies?
Yes — every mailbox has a real receiving address, so you can long-poll for the reply with the same token. Most send-only APIs can't do this.
Last updated June 21, 2026. Spotted something out of date? Email hello@ollastack.com.