I am unsure where to post this question so General Discussion will do. We are using Exchange 2007 and have 2 x CCR mailbox nodes and 2 x HT/CAS servers (CAS not yet NLB'd). We are using a 3rd party solution for the mail gateway. Recently some users have reported they are receiving duplicate emails. All clients are Outlook 2007. This occurs for both internal and external mail. Has anyone seen this before?

i would look at your mail routing. How is the gateway configured to send mail to the Hub Transport servers? Is it sending one email to one hub transport?I would also test SMTP traffic from the hub transport servers. Follow this link: http://technet.microsoft.com/en-us/library/bb123686.aspx and then send a test message to yourself from hub1 and then hub2. Then do that process from the gateway server and see what happens. There is a mailflow trouble shooter: http://msexchangeteam.com/archive/2006/08/07/428616.aspx that you could use to trouble shoot mail flow as well. My guess would be an issue from the gateway to the Hub Transport server.Another thought, cache mode being used? What happens if users go into OWA, are emails duplicated there as well?BP

Yes currently sending to one hub only. Mail delivered correctly from both hubs. Mail delivered correctly from gateway. The mailflow trouble shooter doesn't address the duplicate mail issue I am seeing I think we can say from the above tests that it is not a gateway issue. Cache mode is not enabled. Email only appears once in OWA. Looks like a client issue, thanks for your help.. I didn't think to check OWA. I will recreate their mail profiles and go from there.

Glad I could help! Good luck!BP

Hi,Yes, from the description, the cause of the issue most likely is the client side. Sometimes, the third party Add-in in Outlook can cause this issue. You can check this issue by running Outlook in Safe Mode.ThanksAllen

Hi there,Have you found the cause and solution for this problem?We have the same Exchange server settings as yours (but CAS are NLB'd).So far only duplicate internal email messages are reported; there's none that involves external mail gateway yet. Thank you.