hi all, I have an internal user trying to send an email to a distribution group in my company. The distribution group should not receive email from external senders so I have left the option ticket where all senders are authenticated the internal user is unable to send to the above group - the error below is in message tracking 550 5.7.1 RESOLVER.RST.AuthRequired; authentication required I do not understand this as the user is authenticated thanks

what client is used to send the message?

hi, All internal users can't send message to the DG or only the one user? May be the user miss some permission. Please try the method in below link: http://social.technet.microsoft.com/Forums/en-US/exchangesvrtransport/thread/a003ab77-1819-43a7-b4e3-3b85060a034a/ See if it can help you resolve your issue. hope can help you thanks, CastinLu TechNet Community Support Please remember to mark the replies as answers if they help and unmark them if they provide no help. If you have feedback for TechNet Subscriber Support, contact tnmff@microsoft.com