Postmark specializes in reliable transactional email delivery — think password resets, receipts, and notifications. It maintains dedicated sending infrastructure (separate from marketing email) to maximize inbox delivery rates. Features include DKIM/SPF/DMARC support, bounce and spam complaint tracking, click/open tracking, HTML + text templates, and message streams for organizing different email types.
https://api.postmarkapp.com
Auth type
API Key Header
Auth header
X-Postmark-Server-Token: YOUR_SERVER_TOKEN
Rate limit
50 requests/sec
Pricing
Free tier available
Free quota
Free forever
Documentation
https://postmarkapp.com/developer
Endpoint status
Live — HTTP 200 — endpoint is accessible1.83s
(checked Mar 29, 2026)
Builder score
B
77%
builder-friendly
Pass your Server API token in the X-Postmark-Server-Token request header. Find it in Postmark → Server → API Tokens.
X-Postmark-Server-Token: YOUR_SERVER_TOKEN
| Plan | Price/mo | Included |
|---|---|---|
| Free | Free | 100 emails/mo |
| 10k/mo | $15 | 10,000 emails/mo |
| 50k/mo | $50 | 50,000 emails/mo |
| 125k/mo | $87.50 | 125,000 emails/mo |
Free: 100 emails/mo. PAYG: $1.50/1k emails. Monthly: from $15/mo (10k emails). Volume discounts start at 300k emails.
| Method | Path | Description |
|---|---|---|
| POST | /email |
Send a single transactional email |
| POST | /email/batch |
Send up to 500 emails in one API call |
| POST | /email/withTemplate |
Send email using a stored template with variables |
| GET | /messages/outbound |
List sent messages with delivery status |
| GET | /bounces |
List bounced emails with bounce type and detail |
| GET | /stats/outbound |
Delivery stats: open rates, click rates, bounces |
curl "https://api.postmarkapp.com/email" \
-H "X-Postmark-Server-Token: $POSTMARK_SERVER_TOKEN" \
-H "Content-Type: application/json" \
-X POST \
-d '{"From":"sender@example.com","To":"user@example.com","Subject":"Your order is confirmed","HtmlBody":"<h1>Order #1234 confirmed!</h1>","MessageStream":"outbound"}'
{
"To": "user@example.com",
"SubmittedAt": "2024-03-15T10:00:00.0000000-05:00",
"MessageID": "b7bc2f4a-e38e-4336-af2d-1b5e6c9b4ed5",
"ErrorCode": 0,
"Message": "OK"
}
Data sourced from API Map. Always verify pricing and rate limits against the official ActiveCampaign documentation.