We're in the process of migrating from FirstClass (FC) 5 to Zimbra. Our interim solution is to have both our FC server and Zimbra server running concurrently.

As mail comes to our network it enters our spam catcher, which is configured to pass all email to our Zimbra box. We're a small college and have 200+ new students entering this fall. So on the Zimbra box we've created full user accounts for all new students and created aliases in Zimbra to pass email for current FC users on to the FC server.

The problems lies with our current FC users trying to send email to any of the new students who have full accounts on Zimbra. Short of manually creating either limited user accounts on FC to forward all new student email back to the Zimbra box or hack some sort of FC multiple public list/conference we're stuck on how to make an interim solution.

So if you've successfully migrated to Zimbra from FirstClass please let me know if your situation was at all like what I've described. And as usual, if any of this is unclear please ask and I can provide more detail.