co-domains when email is hosted on another server

[jdg]

I have a site setup as follows:

site: www.domain.com
co-domain: domain.com

The e-mail for this site is hosted on an exchange server at a different location. If I try sending e-mail from a different site on the ispconfig server (using roundcube webmail), it fails to sent. I believe it's failing because it's looking on the ispconfig server for the user being sent to and that user doesn't exist.

If I remove the co-domain, the e-mail seems to deliver from the isp config server to the exchange server. But if I do that, people can't access the site without the host name anymore (http://domain.com).

Is there a way to keep the co-domain (to allow both http://www.domain.com and http://domain.com) and allow email delivery to a different server?

Thanks in advance.

[till]

Set the co-domain to external mailserver on the options tab of the co-domain.