Office 365 Outlook missing some random emails

For the last week or so before, I have been getting complaints about never disappearing or not receiving emails. It seems to be just only one email at a time that they cannot find, which I have no idea where even to start.
We have Office 365 and all the users with Business Premium and ProPlus subscription. Outlook in the user desktop as well as mobile phones. Only certain users have access to OWA, and I have noticed that the OWA users can find the missing email on OWA, but when they search it on Outlook, results come up empty.
I thought it was a syncing issue, but what doesn’t make sense to me is that the email is sitting on OWA, and when I force sync on Outlook, the email fails to pop up on Outlook. Any thoughts?


If you can find the emails in OWA, but not Outlook, the issue might be with your local cached copy stored in the .ost file.
I have seen this loads of times and my advice is to untick the cached exchange mode shown below.

Or, create a new mail profile in the control panel. You can keep your existing mail profile and force the system to ask which one to select.


Also, check your disk for any hardware errors and give it a good defrag if performance is an issue when indexing.


To isolate your concern, we’ll need the following information:

  • Have you tried moving the message instead of dragging it?
  • Are you experiencing this issue on all the messages/contacts on your inbox?

We suggest you to create another user profile and check if the issue still persists.

Let us know how it goes.

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