I had an ubuntu server with 8.04LTS upgraded to 10.04LTS (not quite making it to 12.04, but that’s in the works) with webmin, LAMP, postfix, etc. I used webmin to install dovecot after I already configured postfix to receive mail without requiring SSL with plaintext. It’s an internal only server used to testing purposes, so I don’t mind if someone is sniffing the test passwords that only apply to this box.

Anyway, I was receiving the following in my /var/log/mail.err

Oct 17 08:35:33 SERVERNAME dovecot: POP3(USERNAME): mail_location not set and autodetection failed: Mail storage autodetection failed with home=/home/USERNAME
Oct 17 08:35:33 SERVERNAME dovecot: POP3(USERNAME): Fatal: Namespace initialization failed

Great. Brief search tells me that dovecot’s automatic detection failed (duh) and the fix is to enable the mail location in the configuration file
nano /etc/dovecot/dovecot.conf
Find #mail_location
Assuming it’s commented out, I just added the following below the line:
mail_location = maildir:~/Maildir
Save and close
/etc/init.d/dovecot restart