Parallels

Resolution

Please, add the following lines at the end of /etc/courier-imap/imapd and
/etc/courier-imap/pop3d:

AUTHMODULES="authpsa"
MAILPASSWD="$QMAIL_ROOT_D/users/poppasswd"

Then restart courier-imap service.
 
$QMAIL_ROOT_D could be found in the /etc/psa/psa.conf configuration file.