I'm the server administrator.
Your solution with the 2096 works, but I would like to enforce https for webmail, and I'm unable to do this.
In tweak settings, I have checked the "Always redirect users to the ssl/tls ports when visiting /cpanel, /webmail, etc" but :
1/ When I access webmail.mydomain.com, it does not redirect me to the https version, I stay on http
2/ If I do
https://webmail.mydomain.com I have an error, unable to continue.
I guess I miss some settings for my "subdomain" webmail, to handle ssl, perhaps because the webmail port is not the standard https port

How can I fix this ?
Another thing, I would like to enforce my users to use pop3s and imaps instead of pop3 and imap, so I can disable the standard version.
What I find strange though is that when I enter webmail and click on the mail client parameters section, I have those lines :
Serveur de courier entrant mail.mydomain.com
Serveur de courier entrant (SSL) geg-rbx.ovh.net
Serveur de courrier sortant :mail.mydomain.com (le serveur exige une authentification) port 25
Serveur de courrier sortant : (SSL) mail.root (le serveur exige une authentification) port 465
How comes I have such strange behaviours for the SSL version of the pop3 and smtp? I would like mail.mydomain.com for the SSL versions. How can I fix this? Those geg-rbx.ovh.net and mail.root are wrong
Thanks