Custom Email Domain

Hello,
I have many websites hosted on one server. Only few uses the email option. I would like to create a link like email.domain.com for them to login instead of login using mycyberpanelurl/snappymail. Is there anyway I can do that so that customer also feels like they are logging in through their own website? Looking forward to your suggestions. Thank you.

You can issue a host name ssl and then you can use that but not every user can login via their site URL will be one for all