400 Bad Request error message

Question

Hi,

Since today I've been unable to connect to Oulook on the web. I always get the 400 Bad Request error message. Is there a technical issue at Microsoft today?

Answer 1

Hello LAMOUREUX Franck,

Apologies for the delayed response.

Just an update on this thread. The service incidents EX609725 and EX610644 have been reported resolved. But it may take sometimes on all global tenants. Please check the result after a couple of hours. In case you still experience the same issue, please respond to this thread and we will gladly assist further.

Thank you again for your precious time and kind cooperation.

Sincerely,

Ashraf.

Answer 2

Dear LAMOUREUX Franck,

Good day! Thank you for posting in the Microsoft Community.

I'm sorry for the inconvenience this has caused. Checked from my side, and this has been reported as a service incident for users while trying to access Outlook web. Please refer to the details below.

================================

1. Incident SI: EX610644

Title: Some users may be unable to access their Exchange Online mailbox using Outlook on the web
User impact: Users may be unable to access their Exchange Online mailbox using Outlook on the web.
Current status: We're reviewing service monitoring telemetry to isolate the root cause and determine the next mitigation steps.
Scope of impact: Impact is specific to some users who are served through the affected infrastructure attempting to access their Exchange Online mailbox using Outlook on the web.

================================

2. Incident SI: EX609725

Title: Users can't access Outlook for the web using a specific vanity URL
User impact: Users can't access Outlook for the web using a specific vanity URL.
More info: Affected users may see the following error:

"500: Something went wrong."
Where possible, users can bypass impact by accessing Outlook for the web service directly via "outlook.office.com", or by leveraging the Outlook desktop or mobile apps.

Current status: After reviewing associated logs, we see a behavior occurring where during the authentication process, users are redirected from the vanity URL back to the original domain name, which results in the access request being denied. We're continuing to investigate what is causing this behavior and reviewing potential remediating actions.
Scope of impact: Your organization is affected by this event, and any user attempting to access Outlook for the web using the affected vanity URL is impacted.

Admins can view current information and updates on Service health dashboard in the Office 365 admin center (Service health - Microsoft 365 admin center).

For affected customers to easily identify the information here, this thread may be closed. You may subscribe to this thread or refer to Service Health dashboard for updated information. I will also post back here once the issue is resolved on SHD.

Thank you for your kind understanding.

Best Regards,

Ashraf.