We are running exchange 2007 Sp3 this past week specific user in our environment reported that he got a time out nondelivery.
When checked in message tracking in exchange i found that day an error message " 755268"
When i reviewed the NDR..
Final-recipient: RFC822; firstname.lastname@example.org
X-Supplementary-Info: < #4.4.7 smtp;550 4.4.7 QUEUE.Expired; message expired>
X-Display-Name: bob (email@example.com)