cPanel uses self-signed SSL certificates by default when you connect to the server for cPanel/WHM/Webmail/Exim/Dovecot/FTP

 If you try to connect using a mail program with SSL settings, you will get certificate warnings when you connect to a self signed certificate

 You can either: 

a) Manually accept the certificate and the mail program should allow you to make a permanent exception so you are not prompted with the warning every time

b) Use non-ssl settings in the mail program

c) Purchase and install a signed SSL certificate for the cPanel servers services (cPanel/WHM/Webmail/Exim/Dovecot/FTP) normally for the servers hostname. We have SSL certificates available for $99 covering two years.