451 5.7.3 Cannot achieve Exchange Server authentication Issue

I have 2 Exchange 2007 client access/hub transport/edge servers. Both were operating fine. Lets call them exg01 and exg02. Well, today, I disabled the send connector for exg01 and later noticed that we were getting delivery delay reports. In looking at the queues, I see that there are several hundred outbound messages that exg01 was attempting to relay to exg02 and failing with 451 5.7.3 Cannot achieve Exchange Server authentication. I ahve already checked my default recieve connectors for each server to ensure that TLS and Exchange servers options were enabled like I had seen suggested in other forums.

Any idea whats going on here and how to resolve?
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alaskowskiAuthor Commented:
I just solved this myself. My problem was that I never restarted the Exchange Transport Service after an earlier issue I had. Restarted it and presto! Always the simplest thing you overlook!

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