We have a exchange 2016 server with some mailboxes and also use Rackspace email service with same mailboxes as on Exchange server. The MX record for the domain is pointed to Rackspace server, so when I send an email from exchange(OWA/ outlook) to a mailbox ( on both exchange and Racspace ) the email goes to exchange server despite of the MX record.
How can I force Exchange server to use MX record rather than just routing email to internal mailboxes?
Best Answer
You can't.
Exchange will never use MX records for internal email. If the email address is matched to a mailbox on the server, then it will deliver to that mailbox without any DNS lookups.
You need to review your configuration, which as it stands will not work. The only service that allows you to mix cloud and on premise is Office365.