hello i have a situation were a user received a notification stating that 'delivery has failed to these recipients or distribution lists' even though the recipient had received and already responded to the message. im curious as to why this would occur and i need to provide an explanation to my end user as to why this happened as well. has anyone dealt with a similar situation ?

Hi, Please look at the following article: Troubleshooting Mail Queues That Are Increasing on Edge Transport Servers http://technet.microsoft.com/en-us/library/bb851512.aspx Understanding DNS Query Failure Sensitivity in Exchange 2007 SP1 and SP2 http://technet.microsoft.com/en-us/library/bb676467.aspx Also please check the DNS settings(NIC) for Hub server. You can clear the setting and test the issue again. Please ensure that you have select "Use network card DNS settings on the Internal DNS Lookups tab in the properties of the Hub server in question and verify that "(All Available)" network adaptors is selected in the drop down list. Please try to create Send connectors for the affected remote domains. Then configure the Send connectors to use a smart host for the remote MX records. Note: when we are using Exchange Server on windows server 2008, it will try to ask for AAAA record when we try to send email to remote domain from a DNS server.However, either some DNS servers ignore the AAAA query or they return an unexpected response. This problem occurs because Exchange Server 2007 does not use MX or A records. Besides, this issue has been addressed in rollup 1 for Exchange 2007 SP2.So I recommend you to apply SP2 for Exchange 2007 and then apply rollup 1 for sp2. Exchange Server 2007 Service Pack 2 http://www.microsoft.com/downloads/details.aspx?FamilyID=4C4BD2A3-5E50-42B0-8BBB-2CC9AFE3216A&displaylang=en Update Rollup 1 for Exchange Server 2007 Service Pack 2 (KB971534) http://www.microsoft.com/downloads/details.aspx?FamilyID=de91f994-6263-47ef-89d7-6d344997459d&displaylang=en Regards, Shafaquat AliM.C.I.T.P Exchange 2007/2010, M.C.I.T.P Windows Server 2008, M.C.T.S OCS Server 2007 R2, URL: http://blog.WhatDoUC.net Phone: +923008210320

Hi, Are all the recepients received the email? Is any rule created in the Exchange? Is only one user experiencing this issue? Did you try to send the same recipients by others sender? Thanks Allen