Ned, are you running courier's pop3d or qmail's?
I'm running courier's.
I'm not sure how the courier logger chooses to write to /var/log/maillog tho... I suspect your pop3d is not set to write to this log. ... And I don't know what would be causing the auth errors, maybe a conflict between your pop3d and vpopmail.
I'm pretty shure qmail's pop3d is used for POP, and courier is only used for IMAP.
Vpopmail is set to log only errors to /var/log/maillog.
Well, I'm lost. I guess the next step is to sniff the data that Mail.app is sending and compare it to, say, what Eudora is sending. But that would be a hassle.
ned's key ID is 0x35359C2B