some sent emails are missing and moving to "recover deleted items"

For what it's worth, its 26 Januari 2026 and i am struggling with this issue for some of our employees aswell!

I have no fix, but wanted to comment in case this issue has been disregarded as "things we need to fix in Outlook"

For the last month i have been running Search UnifiedAuditLogs on those mailboxes and the results are very vague (MS Fix the subjects not being shown in these logs please) but it seems that all Outlook clients which have the mailbox as a delegate are performing these actions.

At first i was also 100% confident this is a user mistake, we would recover the mails on a daily basis, they did not check the contents, only the subject identified to them which mail definitely should not have been removed.

Today another user reported the same issue, diffrent mailbox. 

I visited the users desk and had a look, recovered the top item which had been deleted about 15 minutes prior. It recovered to Deleted (Regular trash bin) and i got to see the sender, which was the mailbox where the mail resided, i checked Sent Items, that same e-mail was still there..

As a proof of concept i sent myself an e-mail just now, i will head back there in 15 minutes to see if the same has happend again..

Also here, all users on this shared mailbox (makes the investigation even harder) claim to not have deleted the items.

Hopefully i can report back later that it is indeed just about the Sent items / concepts, but i will do a sample test on the remaining items of the Recoverable Items folder.

Good luck for those experiencing the same!