Allow "external" email addresses for a local domain
I have a domain, call it "flapdoodle.org" on a shared CPanel server. This domain has about 10 email addresses associated with it.
I am moving two of those email addresses to an Exchange server, let's say "firstname.lastname@example.org" and "email@example.com". The rest of the email addresses will remain on the CPanel IMAP server.
This is easy to do on the Exchange side of things. My Exchange server becomes the authoritative server in the MX records. Exchange server has a relay feature which allows all email addresses not registered in Exchange to be forwarded to an external email server.
So... jack and jill get handled by the Exchange server while all other flapdoodle email addresses are forwarded to mail.flapdoodle.org. Works great.
Here's the problem. If someone on the CPanel IMAP server, let's say ralph@flapdoodle,org, sends an email to jack or jill, the email is handled locally so no email ever gets sent out to the Exchange server. The mail is delivered to the local mailbox.
I've got a workaround that allows me to auto forward jack's email to "firstname.lastname@example.org".
But what would be real useful is the ability to mark a local domain email address as "external" so that the email server would send the email instead of processing it internally.