We currently have a fax server deployed in our network, in conjuction with our Sendmail server.

The Sendmail mailer table is configured such that any emails (with fax attached) with a 'faxserver.com' domain are forwarded to the fax server (192.168.1.xx) which then strips off the attachment and faxes it.

I am impressed with what you have achieved with Zimbra, but want to know whether the above can be configured in Zimbra?