I don't know which upgrade causes the issue.
I'm on Ubuntu 14.04 and now i-mscp 1.2.8
When I was in 1.2.2 I was able to connect to IMAPS/POP3S and SMTPS with the same certificate I use for the panel.
I even made a screenflow recording the installation of an account in GMAIL using the POP3S to my server.
A user called me today as she is unable to connect the same way I did in the video.
I checked and indeed Gmail told me the connection uses a self signed certificate and not the one I'm using for the main domain.
I've no idea where I have to look to change this behaviour.
When I test the certificate it seems Dovecot does not use the same certs as the webserver of the panel.
Test of the cert on the panel :
Test of the cert on the pop3 server :