Outlook 2007 periodically disconnects from Exchange 2010 CAS - OWA works

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HWH Support

We are in the process of migrating from Exchange 2003 / Outlook 2003 to Exchange 2010 / Outlook 2007. Out of our 200 users 95% are on Outlook 2007 and 70% are on Exchange 2010. Outlook Anywhere seems to work fine 99% of the time for all users. OWA works well inside the network and via the internet.

Our problem is this. A random user will complain, out of the blue, that their outlook client has lost connection to the server. When this happens, we've seen it prompt for a password or just refuse to connect. If the credentials are provided or not it will still not connect. Keep in mind that this same computer was working just fine for the previous hours and days and weeks. Some random period of time later, 5 - 60 minutes, the Outlook client will reconnect and the user can again work normally. Throughout the disconnected time the user can reliably connect via OWA.

If I launch Outlook and ctrl+click the system tray icon and choose connection status, it lists just the CAS server with a state of disconnected. The connect button will cause a second entry to quickly appear and then disappear and the original entry will flash connecting then go right back to disconnected.

My research has turned up some blog posts to a similar problem within Exchange 2007 that spoke of an IPv6 issue. However further research lead me to believe that 2010's integration with IPv6 would not allow the same " turn off IPv6" solution that " solved" the problem with Exchange 2007.

As background data, we're also seeing issues with messages randomly getting hung in various users outboxes that we can clear up by restarting Outlook and forcing a send/receive.
Any help and insight is greatly appreciated.

Johan Veldhuis [MVP]


Can you give some additional information about your environment: how much CAS servers, is NLB used etc. Besides this perform an automatic configuration test by ctrl+click the Outlook system tray icon and post the output here.



Exchange-blog: www.johanveldhuis.nl

Khoj Sahiwala

Are you receivign an event 9646 , By default if the rpo connections exceed to 32 it disconnects the client until the connections are resetted. This was very prevalent in Exchange 2003 though .

You can check for get-logonstatistics for that particular mailbox and get the details as the connected mailbox getting disconnected and not connecting again points to this issue.

You can also use exmon
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