I’ll edit my post in the other topic because it is not correct.
No, a web domain and a mail domain and two different types. Maybe you didn’t add support for mail domain when creating a web domain and viceversa.
Yes, the requirement is that you explicitly tell Hestia that the mail domain must use SSL.
No.
When you use the command:
v-add-letsencrypt-domain YourUser example.com www.example.com yes
As MAIL is yes, Hestia will issue a certificate for the sub domains mail.example.com
and webmail.example.com
so it will ignore the aliases, in this case www.example.com
To issue a certificate for the web domain and its aliases the command should be:
v-add-letsencrypt-domain YourUser example.com www.example.com
or
v-add-letsencrypt-domain YourUser example.com www.example.com no