I’m planning a migration from our simple SMTP-based solution (IPSwitch IMail) to Exchange 2007. The migration process will be slow, so both mail systems will need to be accessible at the same time, sharing the same domain space.
Let’s say Joe@company.com is already on Exchange, and wants to send an email to sally@company.com, who is on IMail. How do I set up Exchange so that it first checks for the existence of sally’s mailbox in Exchange, and if it doesn’t find it, it sends the mail to IMail for delivery?
At first, I thought Internal Mail Relay was the answer, but after more reading, this is apparently only for email coming *from* the Internet.
