Hi
we are on exchange 2010 sp2. user is getting below ndr when sending email to DG.
#550 5.7.1 RESOLVER.RST.AuthRequired; authentication required ##
i searched & found below forum thread which explained the issue. But in our case sender is domain authenticated mailbox so delivery restriction settings on DG doesn't come into picture.
can someone help me to find the route cause of issue. i run message trace & found that emails were flowing last week. we haven't had any changes in recent. pls advice.