Not able to log in to Webmail/IMAP

Symptoms

Unable to log in to Webmail/IMAP for example.com . It fails with the below errors:

courier-imapd: info@example.com: chdir(/var/qmail/mailnames/example.com/info) failed!!
courier-imapd: error: Permission denied
courier-imapd: LOGIN FAILED, method=PLAIN, ip=[::1]
courier-imapd: authentication error: Permission denied

or

dovecot: service=imap, user=info@example.com, ip=[127.0.0.1]. Error: opendir(/var/qmail/mailnames/example.com/applications/Maildir) failed: Permission denied (euid=30(popuser) egid=31(popuser) missing +r perm: /var/qmail/mailnames/example.com/applications/Maildir, we're not in group 516)

Cause

Incorrect permissions for the /var/qmail/mailnames/example.com/ directory.


Resolution

Correct permissions should be as follows:

# stat /var/qmail/mailnames/example.com/ | grep Access
Access: (0750/drwxr-x---) Uid: ( 30/ popuser) Gid: ( 31/ popuser)
Access: 2015-12-23 16:59:20.527983735 +0700

Make sure that the /var/qmail/mailnames/domain.tld/applications/Maildir/ has the same permissions.