I have an Exchange 2010 SP1 w/Update Rollup 1 installed. Everything seems to be working fine, but i have one message stuck in the queue. The error is 451 Could not complete recipient verify callout
I tried to google this, but didn't find any real helpful info. I've not seen this one before. Is this a config problem on my end and, if so, how do i fix it? All other outbound messages are going out to other domains without issue or delay. Normally, i wouldn't worry about a single message, but this one is being sent from our organization's President and he will want to know why his email is delayed/not delivered...