webmail.domain.com in the form of customer mail entry is it possible?

Is it possible to post mail with the webmail.domain.com subdomain? is it possible to provide this as a standard with an automatic webmail dns record in each customer domain?

Yes this should do → 2 - SSL For PostFix/Dovecot - CyberPanel

And more detailed guide is available here → Achieve 10/10 Email score with CyberPanel! - CyberPanel

I mentioned customer login mail entry.
for example.
webmail.domain.com/rainloop/index.php
mail.domain.com/rainloop/index.php
How to access from the customer domain name.

example : http://webmail.pratikonmuhasebe.com/ customer email login page
so we can’t do like that.

You can do that How to remove port 8090 from CyberPanel - CyberPanel