ok, I tried it:
created a new site with mail.domain.de and forwarded mail.domain2.de to it via url but it is noit transparent: the url changes! and what about traffic? I have to set traffic limits for the mail. domain, sopplvisiting their webmailwon't get their trafficcounted...
please have a lookat my proposal further up: something like ServerAlias mail.*
I am trying to get it transparent but I am not an apache guru, anyone done it so far? I know I could set it up as an alias like this:
Alias /webmail /var/www/webmail
php_flag register_globals off
Options Indexes FollowSymLinks
but then it would be domain.de/webmail....
the problem with the manual setup of the mail.* example I gave was that it was catching all domains that were not explicitly set on my server, I think I saw a similar post here somewhere concerned about the order of virtualhosts...
I think I have to look that up again