Fedora/Centos (Maybe others) Dovecot configuration incorrect.
For any install using the fedora_dovecot-sql.conf.master file: If you use something other than the full email address for the "login" it does not work correctly. The reason for this is the following portion of the user_query:
WHERE email = '%u' AND disable%Ls = 'n'
Which should in actuality be: WHERE login = '%u' AND disable%Ls = 'n'
Or, for more versatility (and say... Gmail style where you can use the username OR the full email address), this is what I'm currently using in my /etc/dovecot.conf: password_query = SELECT password FROM mail_user WHERE (login = '%u' OR email = '%u') AND disable%Ls = 'n'
user_query = SELECT email as user, maildir as home, CONCAT('maildir:', maildir, '/Maildir') as mail, uid, gid, CONCAT('maildir:storage=', floor(quota/1024)) AS quota, CONCAT(maildir, '/.sieve') as sieve FROM mail_user WHERE login = '%u' AND disable%Ls = 'n'
user_query = SELECT email as user, maildir as home, CONCAT('maildir:', maildir, '/Maildir') as mail, uid, gid, CONCAT('*:storage=', quota, 'B') AS quota_rule, CONCAT(maildir, '/.sieve') as sieve FROM mail_user WHERE (email = '%u' OR login ='%u') AND disable%Ls = 'n'
Which is probably how all of the XXXX_dovecot-sql.conf.master files should be setup since this makes the most sense.