Outlook.com Search and recipient suggestions return HTTP 401 Unauthorized / invalid_token for one specific account

Question

Outlook.com Search and recipient suggestions return HTTP 401 Unauthorized / invalid_token for one specific account

Palle Sørensen 0

I have an account-specific problem with Outlook.com / Hotmail.

Outlook.com mail search does not work. Every search returns the message: “Your request can't be completed right now.”

Recipient autocomplete/suggestions in the To field also do not work.

Important troubleshooting already performed:

The problem occurs on three different computers.
The problem also occurs in InPrivate/Incognito mode.
Another Outlook.com/Hotmail account works correctly on the same computers and browsers.
Sending and receiving email works normally.
Contacts exist and manual contact search works normally.
Expanded People Suggestions are enabled.
Newly used email addresses are present in the exported Expanded People Suggestions data, but Outlook.com does not display them as autocomplete suggestions.

I investigated the problem using browser Developer Tools → Network.

Outlook.com mail search request:

POST https://outlook.live.com/searchservice/api/v2/query

returns:

HTTP 401 Unauthorized

X-BackendHttpStatus: 401,401

Recipient suggestions request:

POST https://outlook.live.com/search/api/v1/suggestions

returns:

HTTP 401 Unauthorized

The WWW-Authenticate response header contains:

error="invalid_token"

and:

X-BackendHttpStatus: 401,401

Other Outlook.com requests return HTTP 200 normally.

Because the problem follows this specific account across multiple computers and browsers, while another account works correctly on the same devices, this appears to be an account-specific Outlook.com backend authentication/authorization issue affecting the Search services, rather than a Windows, browser, local Outlook profile, or local search-index problem.

Could someone from Microsoft please advise how this can be escalated to the Outlook.com backend/Search service team so that the authorization/provisioning state of this mailbox can be investigated?

I can provide screenshots of the Network requests showing the HTTP 401 responses and invalid_token.

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Answer 1

This appears to be a known recurring account-specific Outlook.com backend/search-service problem. There are multiple reports I've been seeing in this community forum across different language locales.

However, I still don't see a published Microsoft service incident, official known-issue ID, or confirmed fix.

I just want to remind you that there's no way for anyone here in the community forum to escalate this issue to engineering. The most effective way is for affected users to send in the feedback directly.

In Outlook.com, go to Help > Feedback > Report a problem.

Provide as much information as possible. You can also include screenshots or a screen recording showing the issue.

I also recommend selecting "Yes" when asked whether diagnostic logs can be shared. These logs contain diagnostic information and can be very helpful to the engineering team when investigating the problem.