We recently got a whole bunch of event log error ID 4031, source: MSExchangeIMS, SMTP Interface Events, saying that something like the target server reported error 550, unrecognized user, or relay denied, or recipient not exist, any idea?
What is common situation that this error will come up?
We do not allow relay, only to our specified domain. Platform: Exchange 5.5 with sp4 on WIndows 2000 AS, sp2.
Thanks in advance