What it does
Postmark sends application email through an API or SMTP, with separate Message Streams for transactional notifications and broadcasts. Templates, delivery activity and webhooks help connect it to an application. Its ongoing Developer plan includes 100 emails per month, with no overages.
A receipt and a release announcement belong in different Postmark streams. A transactional stream handles a message triggered for an individual user; a broadcast stream handles a scheduled message to many recipients. In the API, the MessageStream field selects the route. Broadcast messages require an opt-out link.
The sending integration selects a stream explicitly, using its identifier. A product can send a password reset through the transactional route and a monthly update through the broadcast route without treating them as identical traffic. Streams separate the traffic; they do not guarantee placement in a recipient's inbox.
The free Developer allowance is 100 emails each month and does not expire; it permits no overages. Paid subscriptions add capacity, while received messages and additional sends also matter to the selected allowance. Inbound processing and extended retention depend on the package or add-on.
Registration asks for your full name, work email, username and password. The small allowance suits integration work or a project sending only occasional notifications.
Strengths
- Transactional and broadcast messages use separate sending infrastructure
- The free Developer allowance recurs monthly without expiring
Watch out for
- Broadcast messages require an opt-out link
- The free allowance permits no overages beyond its 100 monthly emails
Best for
- Application teams sending both user-triggered messages and permission-based broadcasts
Sources
- Postmark: Fast, Reliable Email Delivery Service | SMTP | API (Oct 25, 2026)
- A better way to send all your application email | Postmark (Oct 25, 2026)
- Postmark pricing (Oct 27, 2026)
- Postmark signup (Oct 27, 2026)