Postmark vs Retarus Transactional Email

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.

Retarus Transactional Email sends high volumes of transactional messages from business applications through Retarus Enterprise Cloud. It offers REST API and SMTP interfaces, with JSON and SMTP/MIME formats, and direct connections to SAP, Microsoft, Salesforce, and ServiceNow. Retarus reports a delivery rate of 98% or higher and guaranteed processing capacity of 100,000 emails per hour; its Email API page separately states capacity of up to 10 million per hour. Administrators can use the myEAS web portal for dashboards, real-time monitoring, reporting, and configuration. The Email API can locate outbound messages by time, message ID, sender, or recipient and provides status information for the past 45 days. Security features include SPF, DKIM, DMARC, enforced TLS, antivirus multiscan, encrypted attachments, and message signing. Retarus processes data in self-operated centers in Germany, Switzerland, the United States, and Asia. The service is paid, with pricing on request. Its free trial costs nothing for 30 days, permits up to 5,000 emails, caps processing at 200 emails per hour, and excludes load testing.