Hello, I have a exchange enviroment in coexistance mode with exch 5.5 sp4 and exch 2003 sp1, I have been getting complaints from email users that emails sent to them are getting bounced back to the external sender. Here is a sample the recipient is a valid user on the exch 5.5 which is the front end server. Help Plz! Your message did not reach some or all of the intended recipients. Subject: Active Nutrition: Nutrition on the Web; feel full, eat less; smoothie boosts; and more ... Sent: 09/15/2005 11:59 PM The following recipient(s) could not be reached: lnichols@xxxxxxxxxxxxxxxxxxxxx on 09/16/2005 2:48 AM The e-mail account does not exist at the organization this message was sent to. Check the e-mail address, or contact the recipient directly to find out the correct address. <aristotle.Palmdrive.local #5.1.1>