SOLVED:
When creating the custom vhost entry for webmail.domain.tld the close/open virtual host container was missing before the webmail.domain.tld addition.
When creating the custom vhost entry for webmail.domain.tld the close/open virtual host container was missing before the webmail.domain.tld addition.
Quote:# Custom VH settings (if any exist)
# Configuration for WebMail
</virtualhost>
<virtualhost *:80>
ServerName webmail.domain.tld