That was the first problem. FIFO. First In, First Out. That meant a single, slow, legitimate newsletter about accounting software could get stuck behind a test email with a 20MB attachment. It was a traffic jam on a one-lane bridge.
smtp-listener 0.0.0.0:2525 smtp-listener 0.0.0.0:587 password password123 Use code with caution. pmta configuration
Best Practice: Bind listeners to specific internal IPs if the server has multiple network interfaces to segregate internal traffic from external feedback loops. That was the first problem
<domain *> max-message-size 25M queue-type FIFO </domain> First Out. That meant a single
The most powerful feature of PMTA is the ability to tune delivery parameters per destination domain. Large mailbox providers (Google, Microsoft) have strict connection limits.