Can't open outlook web

Omar A 0 Reputation points
2026-10-07T14:23:54.71+00:00

I can't seem to open outlook web version. It just tells me to refresh the page, but I get the same message that I pasted below. It's been like this for a few days now. The outlook app on my phone and PC seem to work fine. 

UTC Date: 2026-10-07T13:48:33.143Z
Client Id: [Moderator note: Personally Identifiable Information removed]
Session Id: [Moderator note: Personally Identifiable Information removed]
Client Version: 20260925004.08
BootResult: transient
Back Filled Errors: None
err: Microsoft.Exchange.Data.Storage.MailboxInfoStaleException
esrc: StartupData
et: ServerError
estack: Error: 500
    at Object.w [as createStatusErrorMessage] (https://res.public.onecdn.static.microsoft/owamail/hashed-v1/scripts/owa.mailindex.81106ece.js:1:806)
    at https://res.public.onecdn.static.microsoft/owamail/hashed-v1/scripts/owa.mailindex.81106ece.js:1:192265
st: 500
ehk: X-OWA-Error
efe: [Moderator note: Personally Identifiable Information removed]
ewsver: [Moderator note: Personally Identifiable Information removed]
reqid: [Moderator note: Personally Identifiable Information removed]
cv: [Moderator note: Personally Identifiable Information removed]

Any help would be appreciated.

Outlook | Web | Outlook on the web for business | Sign in
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  1. Hin Vo 1,280 Reputation points Independent Advisor
    2026-10-07T14:43:02.57+00:00

    Hi @Omar A

    To ensure I fully understand your situation and provide the most effective assistance, I'll need a few additional details, such as:

    May I know if there have been any recent changes on your side, or did this issue appear unexpectedly?

    Does this behavior appear only on your device/account, or have other users in your tenant encountered it as well?

    Based on my research, it looks like the Microsoft.Exchange.Data.Storage.MailboxInfoStaleException error may indicate that Outlook on the web is encountering a mailbox information synchronization issue on the server side, resulting in the HTTP 500 error during startup.

    Since Outlook on your desktop and mobile devices continues to work normally, the mailbox itself is still accessible, which suggests the issue may be isolated to Outlook on the web.

    You could try the following:

    Opening Outlook on the web in an InPrivate/Incognito browser session.

    Using a different browser.

    Clearing browser cookies and cache related to Microsoft 365.

    Testing from another network, if available.

    You could give these a try and let me know if the issue still persists. Any additional findings would be greatly appreciated.

    Was this answer helpful?

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