When installing @Mail in Cpanel-enabled servers, you might have problems with the interface services every now and then - mostly caused by Cpanel's own services. To disable CPanel's Exim, POP, and IMAP services, just create the following files:

/etc/eximdisable
/etc/imapdisable
/etc/cpimapdisable
/etc/cppopdisable
/etc/popdisable

Afterwards, restart your Cpanel services:

% /etc/init.d/cpanel restart

Alternatively, you can turn them off in the CPanel interface in the Service Configuration panel.