Emails dissappearing in the new folder

Question

I created folders to organise my emails by different projects. However, all the emails I moved into the folder starting with “57” have disappeared. In contrast, the emails in the folder named “206” are still there. I tried couple times but it keep happening.

I believe this may be a bug, and I’m quite concerned about the missing emails. Could you please assist me in resolving this issue?

Thank you.

Answer 1

The behavior described matches a known issue where certain system or reserved folders are hidden or behave unexpectedly, causing items stored in them to appear to “disappear.” In Exchange Online/Outlook, folders with specific system-reserved names (such as Files, Files1, etc.) can be hidden by service updates, and any items stored there become inaccessible from normal Outlook views.

A similar mechanism can affect user-created folders if they conflict with system folders or reserved naming patterns. When that happens, messages moved into those folders are not deleted, but the folder (and its contents) can be hidden from Outlook and Outlook on the web.

Because this is a service-side behavior, it cannot be fully fixed from the Outlook.com UI alone. The supported path is:

1. Do not continue moving messages into the problematic folder (the one starting with “57”).
2. Contact Microsoft Support so that support can:
   • Verify whether the folder is being treated as a hidden/system folder in the mailbox.
   • Use tools such as MFCMAPI (on the support side) to move the messages out of the hidden/system folder into a normal, user-accessible folder.
3. After recovery, use a different folder name that does not conflict with any system-reserved pattern.

To contact Outlook.com support, sign in to Outlook.com, select Help on the menu bar, enter the issue (for example, “folder emails disappeared”), then scroll down to Still need help? and select Yes. If sign-in is not possible, use the alternate contact link provided in the Outlook.com support article.

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References:

• Exchange Online hides previously displayed Files and folders
• Outlook.com folders disappear or go back to a previous name