We are using squirrel mail (which has been provided by our county council), for email, but are in the testing phase of migrating from squirrel to exchange.
We have setup all the mailboxes in Exhange 2007 mail console, and have added the squirrelmail email address to each users mailbox (which is causing a problem as follows

When a migrated user (to exchange) uses the GAL, and sends an email to a non-migrated user (on squirrel), the email ends up sitting in the recipitents exchange mailbox, because we setup exchange to recognise the squirrel address).

Is there anyway to setup global forwarding or something like that in exchange 2007 console, so that the GAL can still be used by migrated exchange users to send email to squirrel users, during our migration period?