This is already roadmapped for next month.
We are completely replacing the LetsEncrypt system so that it runs on each server in your cluster rather than centrally - this will improve the speed at which SSLs are issued. It will also provision an SSL for mail.{customerDomain} if the DNS is correctly pointed and this will be automatically added to the mail server, even if it is external to the web server.
At the moment email will work with SSL on mail.{customerDomain} but there will be a self signed SSL warning. If you only have a few domains you need this on, you can install a signed SSL manually under servers -> (choose server) -> ... -> server ssls.
jaysays Also if I import cpanel will it change email password?
All database, email and FTP passwords are preserved.