Lots of questions request for logs, network traces, executing tests both client side and exchange server side related.
Causes: While the mailbox is on Exchange 2010, outlook 2003 will use Exchange 2010s Address Book service to workaround query the legacyDN of target shared mailboxes/calendars that workaround needs to be opened and Exchange 2010 returns this as mungedDNs (not typical legacy exchange DNs) which forces outlook.
We ran in to this very annoying situation for users who still have outlook 2003 (SP3, fully patched) and were moved over to Exchange 2010 Roll.Outlook must be online or connected to complete this action.".In summary (this an adaption of the support case conclusions.For the change to take workaround effect immediately, we need to force AD outlook replication, restart of throttling service, rpcclientAccess service on CAS and MBX servers.This was last summer but I needed to find the time to blog this so that it might help people who also need to find a solution.Edit February 3th 2011: The support engineer published a very content rich blog about all this and other possible causes of the error notification on his TechNet blog: Things you need to know about The connection outlook to the Microsoft workaround Exchange server in unavailable.Outlook Errors, outlook UI, outlook UI Issues recipient side-by-side workaround.It also resets the entire navigation pane so any other issues lingering around are thrown out as well.Edit November 15th 2010: Microsoft released a KB article m/kb/2299468 titled, error message workaround when Outlook 2003 clients try to open multiple shared calendars in Exchange Server 2010: "The connection to the Microsoft Exchange server in unavailable.He has my thanks and it took some time to do all the testing and work trough the results.We found out some interesting things.It doesnt release that until outlook is closed.In order to move ahead, you can try the following workaround : First, close the earlier version of Outlook, and repeat your steps.We investigated and searched for a solution. The issue didnt happen when the mailboxes were on exchange Exchange 2007, issue doesnt happen with versions of outlook higher than Outlook 2003.
The support engineer who worked on outlook this case with me notified me by mail that the article had been released.
We also tried disabling throttling by using null.
Then finally advanced support came in to play, now that was a different ballgame.
You can't connect Outlook 2013 to a 2003 Exchange Server.Were supposed to have some patience before this would work, due to Active Directory replication so we did.When a user with a mailbox on Exchange 2007 or 2010 opens his shared calendars using Outlook 2003 the list is outlook different than what you see in OWA or using Outlook 2007 and outlook Outlook 2010.Status, solved, priority, medium, security, public, views 13824.Outlook must be online or connected to complete this action prompts in an Outlook 2003Exchange 2010 world.Viola, it just works!There was not really an indication this would fix anything.And when we pinged m for info they acknowledged the bug and told us that it would probably be fixed in Exchange 2010 SP1.We taught we had a winner here as this could lead to the error while sending and receiving mail keeps working.We even left it overnight.