What version of Exchange are you running? We ran into a weird issue where by default, Exchange 2013 has a default hard limit of 32 EWS connections. So for example, if a user has multiple devices connected to their Exchange account, once that 32 threshold is reached, it just basically stops working. Those connections can include shared calendars, Mac Mail (uses same protocol), home machine if connected to Exchange, shared mailboxes etc. Fix was to increase the connection limit on the Exchange side, which I should add was not recommended, or tell users to close out some of their sessions. Once they fell below that limit, everything started working normally again.
This may not be whats happening to you, but its worth noting just in case. I never thought it would be possible to hit that limit until we had multiple people having the issue. My experience with Exchange and Macs has not been the best, so unless you know whats happening on the Exchange side, or have access to the folks running your Exchange servers, it could be tough to figure out.
I would also suggest watching the logs on a send/receive to see if that tells you anything.
Yes. I still see it under 14.4.4. I have experienced it myself and I occasionally get user reports of the issue. Seems to occur when Outlook has been open for more than 24 hours. I sent a note to our TAM a while back and they thanked us for our feed back. Obviously the issue is not imperative enough to waste expensive support hours with MS on, nor would that probably solve the problem anyway.
We also sporadically experience an issue where after waking from sleep Outlook will ask for credentials but a user can click cancel and it connects up.
This update (14.4.6) provides the latest fixes for Office for Mac 2011. These include the following:
Functionality in Microsoft Office 2011 for Mac
This update fixes an issue that causes a subscription to Microsoft Office 2011 for Mac to change from full retail license mode to trial mode.
Functionality in Microsoft Outlook for Mac 2011
This update fixes an issue that delays Outlook from reconnecting to the network after you resume a MacBook from sleep mode.