Nothing we can do, you are using a self-signed certificate. Get a free certificate using Let's Encrypt
You can use parts of this tutorial to get a certificate: http://forums.sentora.org/showthread.php?tid=2535
Just skip the parts for custom vhost entries and port forwarding, etc. Just make sure you have openSSL, mod_ssl and let's encrypt installed (Info in the tutorial) then update your email settings to use the new let's encrypt certificate
