Postmark
by ActiveCampaign LLC
Developer-focused transactional email API with separated transactional and broadcast streams, templates, and fast delivery. Postmark is a transactional email platform founded in 2009 by Wildbit in Philadelphia and acquired by ActiveCampaign in 2022. As of April 2026, Postmark continues to operate as an independent brand within ActiveCampaign, focused on developer-facing transactional email rather than consumer marketing messaging.
Key Facts
| Attribute | Value | As of | Source |
|---|---|---|---|
| Founded | 2009 by Wildbit (acquired by ActiveCampaign 2022) | Apr 2026 | ActiveCampaign press release |
| Parent Company | ActiveCampaign LLC | Apr 2026 | ActiveCampaign |
| 10K Plan | $15/month (10K plan, 10,000 emails) | Apr 2026 | Postmark |
| 100K Plan | $115/month (100K plan) | Apr 2026 | Postmark |
| Message Streams | Separate transactional + broadcast streams on different IP pools | Apr 2026 | Postmark |
| Developer Tier | 100 emails/month free developer tier | Apr 2026 | Postmark |
| Message Log | 45-day message log retention for debugging | Apr 2026 | Postmark |
| Dedicated IP | Dedicated IP $50/month on 300K+ plans | Apr 2026 | Postmark |
About Postmark
Postmark is a transactional email platform founded in 2009 by Wildbit in Philadelphia and acquired by ActiveCampaign in 2022. As of April 2026, Postmark continues to operate as an independent brand within ActiveCampaign, focused on developer-facing transactional email rather than consumer marketing messaging.
The platform separates transactional (one-to-one application email like receipts and password resets) and broadcast (one-to-many announcements) into different message streams on dedicated IP pools. This separation protects transactional deliverability from broadcast sending patterns and is central to Postmark's reputation for fast, reliable inbox placement. The platform provides message templates with Mustachio syntax, inbound email parsing, webhook delivery for events (bounces, opens, clicks, spam complaints), and a message log that retains content for 45 days for debugging.
Postmark uses volume-based pricing. The 10K plan is $15/month for 10,000 emails, 50K plan $55/month for 50,000 emails, 100K plan $115/month, 300K plan $305/month, and higher tiers available. All plans include both transactional and broadcast streams, templates, and full API access. A 100-email/month developer tier is available for testing. Dedicated IPs are $50/month per IP on plans of 300K and above.
Postmark integrates with Zapier, Make, Segment, and provides SDKs for Ruby, Node.js, Python, PHP, Go, Java, .NET, and Elixir. Common use cases include Rails and Django transactional email, SaaS account emails, and as a drop-in SMTP replacement.
Integrations (8)
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Questions About Postmark
How do you migrate from SendGrid to Resend in 2026?
A SendGrid-to-Resend migration in 2026 follows five steps: verify domains in Resend, port templates (Resend recommends React Email), swap the API client in code, run dual-send for a verification window, and update DNS to point all sending traffic to Resend. Most production migrations take 1-2 weeks end to end.
What does the Resend free tier include in 2026?
As of May 2026, the Resend free tier includes 3,000 emails/month, 100 emails/day, one verified domain, 30-day email log retention, and basic webhooks. The free tier is intended for development, testing, and very small production sends; teams typically upgrade to the $20/month Pro plan once they exceed 100 emails/day.
What's the difference between Resend, SendGrid, and Postmark?
Resend is a React-template developer-first email API from 2023 with 3,000 free emails/month and $20/month for 50K. SendGrid is the high-scale market leader from 2009 (Twilio) with marketing plus transactional from $19.95/month. Postmark is the deliverability specialist from 2010 (ActiveCampaign) for transactional-only at $15/month for 10K.
How do you send transactional email with Postmark in 2026?
As of April 2026, sending transactional email with Postmark requires creating a Server (per-app isolation), generating an API token, verifying a sender domain with DKIM and Return-Path, and posting to the `/email` or `/email/withTemplate` endpoint via the Postmark REST API or one of the official SDKs (Node, Ruby, Python, .NET, PHP, Go).