Postmark has introduced an SMTP endpoint, allowing users to send messages through Postmark's servers using a widely supported protocol. This is not a replacement for their REST API, which remains the preferred choice for sending email through Postmark due to its control and ability to add features that are not possible with SMTP. The SMTP endpoint is ideal for users who already have an application in place that sends email using SMTP or have legacy applications that they do not want to change. To use the SMTP endpoint, users need to configure their SMTP credentials and connect to Postmark's servers on port 25. Some features available only through the REST API are not supported over SMTP, including tagging emails and encrypting communications channels.