Thank you Don. Your suggestion was just what the doctor ordered.
I was able to get it to work but this may only work for my specific situation. I created the redirection as follows:
./sxaa --user Glenney --redirect
mikeg@oldserver.example.com --title migration
I then edited /etc/hosts and put in an entry for my old mail server:
1.2.3.4 oldserver oldserver.example.com
Mail is redirected from the new Scalix server to our old Postfix server. The reason this works is because my old server is Postfix and it allows you to send an e-mail to <username>@<server hostname> and it'll be delivered to the right inbox. Other mail servers may allow this as well. I know QMail will and I'm pretty sure Sendmail will also.
The only other problem I had is that redirected messages recived by my old server have "undisclosed-recipients:" in the To: field instead of an email address. I imagine this is a problem with my Postfix server, not Scalix This an annoyance but not a show stopper. I still may go this way instead of migrating everyone at once.
If anyone know of a better way to accomplish all this mess please post it here.
Thanks,
MG