Postmark
Transactional-only email API with the strongest independently-tested deliverability of any platform reviewed.
Postmark deliberately refuses to send marketing/bulk email on the same infrastructure as transactional mail, and enforces that at the account-approval stage. That focus is the whole pitch: keeping their shared IP pools clean of newsletter/blast traffic is what drives their deliverability numbers. It's priced as a premium for that guarantee rather than competing on cost.
Pros
- +Best independently-tested inbox placement of the group: 83.3% inbox / 1.0% spam vs. 77.1%/20.0% for Amazon SES
- +Transactional-only focus means no risk of a marketing sender tanking your reputation
- +Strong reputation for developer experience and support
Cons
- −Most expensive per email at low-to-mid volume of any provider reviewed
- −Account approval process can restrict use cases that look like marketing/bulk
- −Whitelist/blacklist controls are comparatively less granular than SMTP2GO’s
Pricing
Developer (free)
$0/mo · annual commitment
Month-to-month: not published
- ✓100 emails/mo
Basic
$15/mo · annual commitment
Month-to-month: not published
- ✓10,000 emails/mo
Platform
$18/mo · annual commitment
Month-to-month: not published
- ✓10,000 emails/mo, lowest per-email rate
Specifications
| Rating | 4.4 |
| Features | |
|---|---|
| Inbox rate (3rd-party) | 83.3% |
| Automation Builder | No |
| Dedicated IP | ✓ |
| A/B Testing | No |
| Source IP allow/deny* | No |
*Source IP allow/deny listing: whether you can restrict which IP addresses may use your sending credentials (SMTP/API), checked against each vendor’s official documentation, 2026-09-01. SendGrid, Mailgun, SMTP2GO and SparkPost offer a native allowlist (no denylist); Amazon SES has no native switch but achieves both allow and deny shapes through IAM policy conditions. Postmark, Resend and Mailjet document no such control.
Researched and drafted with AI assistance; reviewed and approved by Tim Meredith. How we use AI
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