leomanf
.. but if you try, you can not point the subdomain "http://webmail.domain.com/" to the bay's default of roundcube since it does not appear in the server manager.
OK you said it was a ibay.
If it's not there in the domains panel then it must not be an ibay, and I would assume from comment in the wiki, that it is in /opt/roundcube
As said previously you need to alter templates to fix this.
Have a look at the templates that were setup by the rpm when it installed.
You can look inside the rpm using midnight commander (mc) to see what gets added to your system
You should also read
http://wiki.contribs.org/Web_Application_Redirect_Tutorialas it gives the concepts of how these things are done for Joomla, but the same concepts apply to roundcube, just change the names and locations etc.