I've been using Mail.app for 2.5 years with no prob. Suddenly it's started deleting about 50% of messages downloaded from the server (POP account) as soon as they're downloaded. It plays the "new message" sound, but the message is nowhere to be found. Mail.app marks the messages on the server as received.
I'm using G4 mirror door running OSX 10.3.9. I've tried re-booting, of course... and throwing away the Mail preferences then re-creating them. I've also changed the pref to hold messages on the server for a week after they've been "picked up" to ensure I don't miss any.
Workarounds include turning off Mail.app and forwarding all messages on the server to myself. Then when I first turn on Mail.app it downloads all the new messages properly. I must keep Mail.app turned off and re-start it in hopes of retrieving most of my messages. Of course, using my webmail account is the only way to ensure I see all my messages. That's not the option I like.
Any suggestions?