Shared Mailbox - .ost does not update

Copper Contributor

Hello all,

we use Exchange Online including shared mailboxes and have a somewhat strange problem.

In order for the search function to work properly in the shared mailbox, we have given permission to the appropriate users and they can then add the mailbox via their credentials in Outlook. This creates an .ost file (would not be the case with "only assigned mailboxes) and the search function works much better.


However, we now have the phenomenon that exactly this .ost file does not synchronize properly and therefore we cannot send any mails. Sometimes it is enough to restart Outlook to solve the problem (.ost is then up to date again), but sometimes you have to restart the whole PC (Windows 10 - 22H2).

Outlook version is 2303.

On the screenshot you can see hopefully quite well what the problem is.




This occurs with different users with the same mailbox.



2 Replies
How large is the mailbox/ost? And what's the sum across all accounts used in the same profile? Generally, aim to keep individual OSTs under 10GB.

the mailbox is only 2 Gb in size and it is used by about 5 people.