[Dovecot] Mailbox isn't a valid mbox file

Hello all,

I have a new installation of Fedora 4 and Dovecot 1.4.Alpha4

A small percentage of my users are getting unable to pop mail from a client (ie: Outlook), they get continually prompted for username/password. The error they get is: Mailbox isn't a valid mbox file.

When I look in the file, I don't see anything unusual. There's not much info on the Internet about this problem. The only thing I found mentioned blank lines in the file. So, I tested and found that I'm able to get mail on other accounts regardless of whether there are blank lines in between messages.

Thanks,

Cliff