[Dovecot] AuthenticationFailedException: [IN-USE] Couldn't open INBOX: Permission denied

[Earles, Jill]

I've been pouring over the documentation for dovecot, but can't find a solution to this problem.  I recently took over administration of the dovecot email service at the University where I work, and things were going smoothly.  We've been creating email accounts for use with JIRA, a bug reporting/tracking system, and one day recently, when I tried to add a new account to JIRA, I got this error returned from dovecot:

"AuthenticationFailedException: [IN-USE] Couldn't open INBOX: Permission denied"

I got help from Atlassian, the creators of JIRA, and they sent me links to some forum posts that said that changing the permissions of that user's /var/mail/ directory to 0600 would solve the problem.  I changed that and no longer got the error.  

Being satisfied that this was a solution, I created a bunch of new email accounts today to replace exchange accounts, and then changed the permissions on all the /var/mail/ directories to 0600.  Now I'm getting that error again, even for pre-existing email addresses, including the one that I had previously fixed by changing the permissions the same way.  I tried changing some of the older accounts back to 0660, which is what they had before, and I still get the error even after restarting dovecot.

JIRA uses POP, port 110, to connect to the dovecot mail server.  I've also had the same problem trying to connect from Mac Mail.

Our JIRA application is used for tracking issues for the UBC Libraries, and those email addresses are critical for the creation of tickets and adding comments to tickets.  I am at a loss for what to do.

Can anyone help?  Thank you very much for your time.

# dovecot -n
# 2.0.9: /etc/dovecot/dovecot.conf
# OS: Linux 2.6.32-131.0.15.el6.x86_64 x86_64 Red Hat Enterprise Linux Server release 6.4 (Santiago) 
auth_debug = yes
auth_debug_passwords = yes
disable_plaintext_auth = no
mail_access_groups = mail
mail_location = mbox:~/mail:INBOX=/var/spool/mail/%u
mail_privileged_group = mail
mbox_write_locks = fcntl
passdb {
  driver = pam
}
ssl_cert = </etc/pki/dovecot/certs/server.crt
ssl_key = </etc/pki/dovecot/private/server.key
userdb {
  driver = passwd
}
protocol pop3 {
  pop3_uidl_format = %08Xu%08Xv
}

Here's an except of the maillog from a recent attempt:

May  8 17:46:49 moose dovecot: auth: Debug: pam(lib.sysadmin,{ip removed}): lookup service=dovecot
May  8 17:46:49 moose dovecot: auth: Debug: pam(lib.sysadmin,{ip removed}): #1/1 style=1 msg=Password:
May  8 17:46:49 moose dovecot: auth: Debug: client out: OK#0111#011user=lib.sysadmin
May  8 17:46:49 moose dovecot: auth: Debug: master in: REQUEST#0111028653057#01128298#0111#011a60ed90501af39d7e353a14e027255cd
May  8 17:46:49 moose dovecot: auth: Debug: passwd(lib.sysadmin,{ip removed}): lookup
May  8 17:46:49 moose dovecot: auth: Debug: master out: USER#0111028653057#011lib.sysadmin#011system_groups_user=lib.sysadmin#011uid=523#011gid=524#011home=/home/lib.sysadmin
May  8 17:46:49 moose dovecot: pop3-login: Login: user=<lib.sysadmin>, method=PLAIN, rip={ip removed}, lip={ip removed}, mpid=28302
May  8 17:46:49 moose dovecot: pop3(lib.sysadmin): Error: stat(/var/spool/mail/lib.sysadmin) failed: Permission denied
May  8 17:46:49 moose dovecot: pop3(lib.sysadmin): Error: stat(/var/spool/mail/lib.sysadmin) failed: Permission denied
May  8 17:46:49 moose dovecot: pop3(lib.sysadmin): Error: Couldn't open INBOX: Permission denied
May  8 17:46:49 moose dovecot: pop3(lib.sysadmin): Couldn't open INBOX top=0/0, retr=0/0, del=0/0, size=0
May  8 17:46:50 moose dovecot: auth: Debug: auth client connected (pid=28303)
May  8 17:46:50 moose dovecot: auth: Debug: client in: AUTH#0111#011PLAIN#011service=pop3#011lip={ip removed}#011rip={ip removed}#011lport=110#011rport=64420#011resp=AGJ2YXV3LnJlbGFpcwByM2xAaXMuYnZAdXc=