MX records #1-4 is postini and we had MX #5 as our Exchange 2007 mail server. MX records only control inbound email. Outbound email will use A host records and PTR records so removing MX #5 will not cause any problems with mail flow.
Using Postini for Inbound Filtering of Your Inbound Mail Only
by ray | Feb 2, 2009 | Exchange Mail Server | 0 comments