In cPanel server POP3 not authorizing people to login.
The problem is xinted had two services popa3d and popa3ds, which were interfering with cpanel secure ports as well cpanel’s pop3 service.
remove popa3d and popa3ds from /etc/xinetd.d folder
# mv /etc/xinetd.d/popa3d /etc/xinetd.d/popa3d.bak
# mv /etc/xinetd.d/popa3ds /etc/xinetd.d/popa3ds.bak
restarted xinetd service
# /etc/init.d/xinetd restart
Re-install using /scripts/courierup –force
# /scripts/courierup –force