Ok, yes, so the URL

https://mail.domain.com/essays/... etc responds exactly the same as https://www.domain.com/essays/...

which is a pretty clear indicator that the mail.domain.com is being routed to the same vhost as www. Don't know exactly how this is setup, possibly with a "ServerAlias *.domain.com" or whatever. (it might also just be the first/default vhost)

... in which case, can just set it up in the .htaccess for the main www domain....

RewriteEngine On
RewriteCond %{HTTP_HOST} ^mail.
RewriteRule . - [F,L]

... that makes sure the forbidden is only done on the mail. hostname. And hence make it unindexable.


Don't see anything indexed in webmail.domain.com - so nothing to worry about there. It does seem to be routed to a dedicated vhost (with the webmail app installed!)