Running Exchange 2007 SP2, Outlook 2007 SP2.
One of my users is having problem sending emails to email@example.com. The NDR is "None of your email accounts could send to this recipient". Other users don't have this problem, and the user could send to the recipient a few days ago ok.
I ran message tracking on our Hub Transport server, and there is no mention of my user trying to send to firstname.lastname@example.org, so it looks like the message is not even getting to Exchange, seems to be Outlook blocking it?
Have send KB here, but doesn't apply: http://support.microsoft.com/kb/872896