Why is my Exim SSL certificate changing every day?

Hello, The URL of my mx entry is mx.exmple.net and my SSL certificate is emitted for that URL. Every night WHM changes the certificate to one for the URL of the WHM itself (cpanel.example.net). Then I go to WHM -> Service Configuration -> Manage service SSL certificates and I change the certificate back again. How can I do so that it does not happen again? Thanks in advance