Updating courier-imap configuration

By default, the courier-imap creates pop3 (110), pop3s (995), imap (143) and imaps (993) servers.
Generally, they are not all needed, and for obvious security reasons, it is better to not start useless servers.

Under GNU/Linux Fedora, the corresponding configuration files, which are under /usr/lib/courier-imap/etc/, are respectively pop3d, pop3d-ssl, imapd and imapd-ssl.
Into each, there is a variable XXXSTART (with XXX corresponding to POP3D, POP3DSSL, IMAPD or IMAPDSSL) which can be YES or NO.

To not start such a server, it is enough to replace corresponding YES by NO.

Finally, restart the courier-imap service.