Error TooManyObjectsOpenedException persistent

Question

Hi,

Since this morning i have this error when i tried to access web

UTC Date: 2025-11-26T10:12:51.416Z
Client Id: [Moderator note: personal info removed]
Session Id: [Moderator note: personal info removed]
Client Version: 20251114001.19
BootResult: throttle
Back Filled Errors: Unhandled Rejection: Error: 500:undefined|undefined:undefined
err: Microsoft.Exchange.Data.Storage.TooManyObjectsOpenedException
esrc: StartupData
et: ServerError
estack: Microsoft.Mapi.MapiExceptionSessionLimit
st: 500
ehk: X-OWA-Error
efe: [Moderator note: personal info removed]
ewsver: [Moderator note: personal info removed]
emsg: TooManyObjectsOpenedError

And on my Outlook Client, my email don't synchronize, i continue to receive email that i can check with my phone with outlook mobile, but i can, i'm a adminsitrator, i've already reset 3 times all sessions, reboot my machine and even try to connect to the webview of another machine.

I've disconnected my account of my outlook client and when i tried to reconnect i have this error when i click to copy the informations :

UTC Date: 2025-11-26T10:12:51.416Z
Client Id: [Moderator note: personal info removed]
Session Id: [Moderator note: personal info removed]
Client Version: 20251114001.19
BootResult: throttle
Back Filled Errors: Unhandled Rejection: Error: 500:undefined|undefined:undefined
err: Microsoft.Exchange.Data.Storage.TooManyObjectsOpenedException
esrc: StartupData
et: ServerError
estack: Microsoft.Mapi.MapiExceptionSessionLimit
st: 500
ehk: X-OWA-Error
efe: [Moderator note: personal info removed]
ewsver: [Moderator note: personal info removed]
emsg: TooManyObjectsOpenedError

Answer 1

Hello @Pierre LECOMTE,

Good day! Thank you for posting your valuable question on the Microsoft Q&A forum.

This is an active incident currently being tracked by Microsoft.

We are aware of an ongoing service issue impacting Exchange Online for some users. This issue may cause intermittent failures when accessing mailboxes through any connection method, including Outlook desktop, web, and mobile clients.

Microsoft is actively investigating the root cause of this incident. Analysis indicates that 500-error codes are being returned in HAR traces, and we are working to isolate the underlying problem.

Scope of Impact: Users may experience mailbox access failures or synchronization issues. While some users can receive emails on mobile clients, Outlook desktop and web access may remain affected.

Root Cause: An indexing issue within a section of mailbox database infrastructure caused mailbox state invalidations and client disconnections, resulting in impact.

Mitigation Efforts: Engineering teams are applying targeted fixes and monitoring service health to reduce impact. The problem has not yet been fully resolved and may continue to affect some users intermittently.

If you are an administrator, please monitor the Service Health Dashboard in Microsoft 365 Admin Center for real-time updates. If you are not an admin, let us know, and we’ll provide troubleshooting steps tailored to your situation.

We understand the importance of uninterrupted access to Exchange Online and sincerely apologize for any inconvenience this may cause. Our engineering teams are working diligently to restore full functionality as quickly as possible.

Thank you for your patience and understanding while we work toward a resolution. We will provide updates as soon as more information becomes available.

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