AutoSSL for webmail and mail only

I have a website hosted on another server and I created an account on CWP just to use as an email server. However, when trying to generate an AutoSSL, the generated certificate points to the host.myserver.com subdomain and this causes an error when trying to access webmail.mysite.com. How to solve this problem? Is it not possible to generate a certificate for the webmail and mail subdomains only?

When you create the account, you have to set the domain name as e.g. mail.domain.com

Otherwise the SSL will fail because the domain isn't pointing to CWP.

Then just create your MX record and A records to point to CWP at your DNS provider.

To access webmail, you will have to create a redirect (which CWP usually does automatically in Apache), or just use mail.domain.com/webmail.

This looks brutal: mail.domain.com/webmail 
The best option is to buy a SSL certificate for one year at a price of 6 euros and not deal with nonsense.