One of my users just
started getting NDRs, supposedly due to this error whenever he attempts to
send messages to anyone outside of our domain. As far as I can tell,
the issue is only impacting this single user. When I see him again,
I'm going to have him try sending a message from another machine via OWA.I
haven't done anything on the server side that should have any impact on his
specific account. A sample part of an NDR follows. Thanks for any
ideas: