This user is part of my domain. When sending emails to this user internally they receive the email fine. When sending emails to this user from an external account i receive the error Delivery Status Notification (Failure)Any ideas?Cesar Romero

Make sure that "Require that all senders are authenticated" box is not selected (or unticked) inRecipient Properties > Mail Flow Settings Tab > Message Delivery Restrictions... http://technet.microsoft.com/en-us/library/bb629676.aspxAmit Tank | MVP Exchange Server | MCITP: EMA | MCSA: M | http://ExchangeShare.WordPress.com

I just did that about a minute ago and was getting ready to reply to my own question. Thanks Amit.Cesar Romero

Great!.. :)Amit Tank | MVP Exchange Server | MCITP: EMA | MCSA: M | http://ExchangeShare.WordPress.com