Hello,We have one customer receiving SMTP 550; 5.7.1 message refused when they try e-mailing our domain. Their NDR does not show our domain as the reporting mail relayissuing the error. We have no record of their e-mail being sent (or NDRS being returned) in our Exchange Server logs. We also have no record of them in our Anti-Spam/Anti-Virus logs.The NDR they showed us was: <their-mail.their-domain.com #5.7.1 smtp;550 5.7.1 Requested action not taken: message refused> I would assume that this NDR is being generated on their end. If so, what is it? And, would this NDR have something to do with our domain?Our inbound relay has Exchange 2003 setup on it. We have one SMTP Virtual server. I was reading somewhere that if the "Advanced Delivery" has a FQDN setup as server.domain.local, that this may be a problem for messages being properly relayed to us. If I change this to domain.com, wouldn't that affect the internal communication of the network? Can someone give me assistance to properly setting up the "Advanced Delivery" window? Our public domain is listed as both domain.com and domain.net. How would I set those up? Would I need three SMTP Virtual servers?Please help. Thank you. :)

hi,this is a relay problem.check relay options.http://msexchangeteam.com/archive/2006/12/28/432013.aspxhttp://support.microsoft.com/kb/895853/en-usregards,Mumin CICEK | Exchange - MVP | www.cozumpark.com | www.mumincicek.com

Hi Eric, We can see the NDR is generated by the remote server, the problem occurs in the remote domain. You need to let your customer contact his/her mail admin for further help. Maybe some settings is incorrect in their server. A related article for your reference: 4.What options in Exchange 2003 help us control Relay?http://social.technet.microsoft.com/Forums/en-US/exchangesvrgeneral/thread/d46bf491-0e5b-4b9e-81b3-81c66b6ad81c#4 Thanks, Elvis

We discovered the problem. Symantec Mail for Exchange Software on our end was blocking them. The sad thing is that there was no indication from Symantec that we were blocking them (like logs). Everything was fine when I added their domain to our whitelist.