Horse Tools 1.3.38
- Horse Tools now checks whether your server can reach any other mail server at all — the question nobody asks, and the answer that explains most vanished email. WordPress hands each message to a local mail program, that program accepts it (which is why every screen says "sent"), and then finds outbound port 25 closed. DigitalOcean, Google Cloud and many others close it by default so their machines cannot be used for spam. The message waits in a queue nobody reads, and no bounce arrives, because a bounce would have to leave by the same door.
- This is reported first, above everything else, because no DNS record can change it. A site in this state can spend weeks adjusting SPF while every message goes on sitting in a queue.
- Diagnosed from two sites on one server with opposite DNS — one publishing a hard-fail SPF, the other publishing none at all — both reporting mail sent and neither delivering anything. Different DNS, identical outcome, so the DNS was not the cause. The earlier releases' focus on SPF was right about what those records say and wrong about why the mail was disappearing.
- The check is a bare TCP connect to a well-known mail exchanger, held for half a day. Nothing is sent and no message is involved; it asks only whether the door opens. It is skipped entirely when the site already sends through an SMTP service, because those use a different port.
Install: download horse-tools-1.3.38.zip below, then Plugins → Add New → Upload Plugin.