I had an issue with the mail server when I came to work this past Monday.
I re-booted the server and everyone's mail came up with the exception of one client.
I received the error (from Outlook, using POP3):
"Task 'user@domain.com - Receiving' reported error (0X800CCC92): 'Your e-mail server rejected your login. Verify your user name and password for this account in Account Settings. The server responded: -ERR [SYS/PERM] Unable to process From lines (envelopes), change recognition modes or check for corrupted mail drop.'

I did change the client's password and it still doesn't work.
Any ideas.

That is an error message from qpopper. It occurs when your mailbox has one (or more) corrupted emails. Probably caused by abruptly powering down your Slackware mail server?
Check the mailfile of this person on your Slackware server, using an ascii editor, find the corrupted header lines, delete those (make a backup of the user's mailfile first!) and all should be well again.

Eric

Hey Eric,

I went to the mail file (var/spool/mail/username) and looked at the file using "Jed" command, but with over 1000000 lines in the file, I didn't see anything that stuck out as a corrupted header. Is there something specifically that I should see or that I can search for?

If I find such a header, do I just delete that email (they all seem to run together in that editor) and then just save out of the the file?

Mike