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I am part of an organization that uses Microsoft 365 and Outlook for our mail and we have a user who, when they receive an email from a certain account (lets call it alice@example.com), it gets automatically deleted with no way of recovering it. Our user will get incoming notifications saying that alice@example.com has sent an email, and can read the contents in a preview, but when they go to read the email they find that it has disappeared.

There are no rules deleting it, and as a way to try to fix the problem we created a rule that sends all emails from alice@example.com to the inbox. It did not work.

We thought that the emails may be getting junked or marked as spam automatically, but they fail to appear in the junk or spam folder. The sender is in the "Safe Senders" list in Outlook, and in none of the junk or blocked lists.

Auto-archive is not turned on for the user. Any emails from alice@example.com that are forwarded by other accounts are also deleted.

The user only uses the mobile and web versions of Outlook and signs out of their web email every time they are finished using it, so POP3 happenstances should not be an issue.

Gabe Chantayan
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  • Open a support case with Office 365 from your tenant. It's free. They'll help you resolve the issue. – joeqwerty Dec 02 '22 at 18:04
  • @joeqwerty We've tried that; they were unable to resolve the issue – Gabe Chantayan Dec 02 '22 at 18:29
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    Run a message trace in the EAC for emails sent from alice@example.com to the recipient. That may give you more insight into what's happening. Additionally, open a new support case with Office 365. They can't leave the issue unresolved. That wouldn't be acceptable to me. – joeqwerty Dec 02 '22 at 19:37
  • Does this only occur to a particular user in your tenant? In other words, others in your tenant can receive and view emails from alice@example.com properly, right? Have you tried doing a search within the entire mailbox of the affected user to see if the disappeared mails from alice can be found somewhere. You can also check the "Deleted items" folder and "Deletions"(in OWA, click the Deleted items folder, hit the hyperlink of "Recover items deleted from this folder") to see if any clues can be found. – Yuki Sun Dec 06 '22 at 06:59

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The fact emails Alice sends to other users, which are then forwarded to this user, are also deleted - stinks of an inbox rule to me.

First some stupid/ back-to-basics questions - you said the user only uses web and mobile, but you also referenced rules in Outlook - they aren't always the same. I'd start by using the web only. What happens if you search the inbox for alice@example.com is the new (disappeared) email found? Are any emails from Alice found? Did you specifically check for inbox rules on OWA? I'd be surprised if o365 support didn't check these but - you know - gotta ask.

Change your user's password and initiate a sign-out, in case another client eg outlook is running somewhere.

Did you check transport rules aka mail flew rules? Slightly long shot but possible I suppose. https://learn.microsoft.com/en-us/exchange/security-and-compliance/mail-flow-rules/mail-flow-rules

I agree with the message trace idea, though it may only show as delivered, it might also tell you where it went afterwards. Don't get the farm on it giving you the answer.

If it's not affecting other users in the company i.e. emails from Alice arrive OK then it does suggest it's related to your user. I'd say look at your AV if you were using outlook desktop, but you said the user doesn't use outlook desktop?

Disconnect the mobile client for a short time to confirm but I don't remember there being anything on a mobile client that could do this, it's worth eliminating it.

Jonathan Rixon
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