Postmark vs Sidemail
Postmark
postmarkapp.comSidemail
sidemail.comSide by side
| Figure | Postmark | Sidemail |
|---|---|---|
| Price from | $5/mo | $2/mo |
| Free plan | Yes | — |
| Free trial | Yes | Yes |
| Open source | — | — |
| Web | Yes | Yes |
| API | Yes | — |
| Plans published | 8 | 3 |
| Spec score · Transactional email services | 9.2 (#1) | 7.4 (#33) |
| Spec score · Transactional Email Software | 8.7 (#7) | 7.4 (#35) |
| Sending methods | Postmark supports REST API, SMTP, and multi-region SMTP routing. | smtp |
| Free plan | Yes | No |
| Monthly send limit | 10000 | 2000 |
| Security | Postmark supports TLS and HTTPS, DKIM, SPF, DMARC, two-factor authentication, API permission controls, penetration testing, and DDoS protection. | The site says it uses industry-standard practices to secure user information. |
Plans
Postmark
- FreeFree
- Basic$15 a month
- Pro$16.50 a month
- Platform$18 a month
- Custom activity retention$5 a month
- DMARC monitoring$14 a month
- Dedicated IP$50 a month
- High-volume plansPriced on request
In their own words
Postmark
Postmark delivers and tracks application email as an alternative to SMTP or Sendmail. It separates transactional and broadcast messages into different Message Streams and IP infrastructure. Developers can send through REST API, SMTP, or multi-region SMTP routing, with official libraries for Node.js, Python, Rails, Ruby, PHP, and.NET. Inbound messages can be converted to JSON and sent to a webhook URL. Tracking includes delivery, bounces, spam, opens, and links, with event webhooks. Editable responsive templates cover transactional messages such as password resets, receipts, and invitations. The free Developer plan costs nothing, provides 100 emails per month, permits no overages, and does not expire. Basic starts at $15 a month for 10,000 emails per month; extra emails cost $1.80 per 1,000 and are calculated at the end of the billing cycle. Unused emails do not roll over. Postmark lists API and web access. Its iOS app was sunset in June 2025 and is no longer supported.