Shared Mailboxes not Caching for Exchange Online User

Brass Contributor

Recently users reported that the shared mailboxes they access are not updating.  Upon investigation, it appears that Outlook will not cache a shared mailbox located On-Prem when the user is in Exchange Online.  (This may also be the case for other scenarios, but I haven't tested them)


My On-Prem Server is Exchange 2016 running in Hybrid.  All my users are in the cloud, all shared mailboxes are located on-prem.  Outlook and Exchange is fully up to date.  I suspect it was a recent update that has caused this as it has only been reported in the last week.


I can go to Outlook and turn the cache off for the shared mailbox, and the user can see all the recent mail, obviously this is only useful if the user is often connected to the internet.


Has anyone else experienced this or know of a fix?  I have several users who are not always connected and need access to the shared mailbox.  For logistical reasons moving the mailboxes to the cloud is not currently an option.  That will be done further down the road.



3 Replies


It seems that our environment is facing the same issue. Have you found a solution yet?

Same here (Exchange 2019 Hybrid)
Since a short time, our users (user cloud, shared mailbox onprem), have exactly the same problem. Disabling the cache mode works. But it seems to be a general problem!?