Only one user on a domain couldn’t download new mails. Webmail showed the messages were in his inbox, but Outlook wouldn’t connect and download them. The user tried changing password on the server and setting up the account in Outlook on another PC in the same office. Still no dice.
So I SSHd in to the server:
> grep [username] /var/log/maillog
which showed a load of:
Nov 9 12:21:21 host2 in.qpopper[21141]: [username] at 217.36.***.*** (217.36.***.***): -ERR [SYS/PERM] Unable to process From lines (envelopes) in /var/spool/mail/[username]; change recognition mode or check for corrupted mail drop.
So I searched Google for “change recognition mode or check for corrupted mail drop” and found this page, which stated that in that case: “Aha, a corrupted mail drop file! So, SSH into the server, edit the file at /var/spool/mail/janedoe and I find the first three lines of the file are random garbage”…
So back to the server’s shell and type:
> pico /home/spool/mail/[username]
and there was the problem- a couple of random characters right at the start of the user’s (inbox) file. I deleted those, saved out of Pico and all was fine.
When I spoke with the user afterwards it turned out they’d had some problems with their (BT Supplied) office ADSL line dropping out recently, a couple of times in the middle of Outlook’s Send/Receive, so it’s likely that an unfinished session caused the problem in this case.