ClrStream vs Postmark
ClrStream
mithi.com
Postmark
postmarkapp.comSide by side
| Figure | ClrStream | Postmark |
|---|---|---|
| Price from | — | $5/mo |
| Free plan | — | Yes |
| Free trial | — | Yes |
| Open source | — | — |
| Web | Yes | Yes |
| API | Yes | Yes |
| Plans published | 2 | 8 |
| Spec score · Transactional Email Software | 7.5 (#34) | 8.7 (#7) |
| Spec score · Transactional email services | 7.0 (#40) | 9.2 (#1) |
| Company history | Mithi's company timeline lists ClrStream among its products in 2018 and identifies ClrStream 2.5 in 2024. | Postmark says it has delivered billions of emails since 2010. |
| Delivery methods | both | Postmark supports REST API, SMTP, and multi-region SMTP routing. |
| Integrations | ClrStream integrates with directory services, Vaultastic, ERP, CRM, core banking, and other business applications through APIs and open protocols. | Official integrations include Slack, Zapier, Stripe, WordPress, Supabase, Bubble, Craft CMS, Netlify, and Gravity Forms. |
| Security | The maker describes spam, virus, and malware protection with a 7-layer security architecture and real-time threat mitigation. | Postmark supports TLS and HTTPS, DKIM, SPF, DMARC, two-factor authentication, API permission controls, penetration testing, and DDoS protection. |
| Support | The maker offers access to a help desk, solution architects, and scheduled product demonstrations. | Postmark offers support by email, live chat, and one-on-one calls and reports a 95% customer happiness rating. |
| What it does | ClrStream is an enterprise email notification platform for automating high-volume customer and stakeholder communications. | Postmark delivers and tracks application email as a replacement for SMTP or Sendmail. |
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.