Here is my scenario:
Currently, we have a domain, let's call it XXXX. All of our email addresses however, are firstname_lastname@YYYY.org. We'd like to transition our email addresses to @ZZZ.org. The domain will stay the same (XXXX), just the email suffix will change. However, we'd also like to keep @YYYY.org active for the external world who will obviously still be sending to @YYYY.org.
Is this just adding a new entry into the default recipient policy in Exchange? Making @ZZZZ.org the primary, but still keeping @YYYY.org checked? Any advice would be much appreciated!