Hi @Morten Hansen ,
Welcome to Q&A!
Before going further, may I know what's the version of your Exchange server?
Is this a randomly-occurred issue and whether you can reproduce this issue again? If possible, it is suggested for you to try the same test on your OWA and see if this behavior would also exist there.
And are there any similarities between these 10 missing emails?
In order to further confirm if those missing sent email messages are still in the sender's mailbox, it is suggested for you to try the Search-Mailbox command in EMS and see if we can successfully find them. For example, I searched the mailbox of user01 and copies the search results to the User02 Mailbox in the Inbox folder like below:
By the way, if you can still reproduce this issue, I would suggested you to enable the Mailbox audit logs feature for this problematic mailboxuser and then reproduce this issue to see if it could log any move or remove records.
Any updates, please feel free to post back.
Hi @Morten Hansen ,
Thanks for your reply.
A little bit weird indeed. It's hard to say if this situation is related to the Outlook hang behavior. Considering that we cannot reproduce this issue again, what we can do now to further research about this issue is quite limited. In order to prevent this issue from happening again as much as possible, it is suggested for you to try updating your Outlook to the latest version, keep using for now and see if this issue would re-occur in the future.