What is this error code?

Question

UTC Date: 2026-05-21T15:58:21.911Z
Client Id: AEB50AAE8D784BD5849B9F2CB218C2C3
Session Id: d979a99a-666a-43a9-b358-75045511ea5b
Client Version: 20260508010.14
BootResult: accessDenied
Back Filled Errors: Unhandled Rejection: Error: 500:undefined|undefined:undefined
err: Microsoft.Exchange.Data.StoreObjects.AccessDeniedException
esrc: StartupData
et: ServerError
estack: Error: 500
    at Object.w [as createStatusErrorMessage] (https://res.public.onecdn.static.microsoft/owamail/hashed-v1/msalv5/scripts/owa.mailindex.0f9cc403.js:1:806)
    at https://res.public.onecdn.static.microsoft/owamail/hashed-v1/msalv5/scripts/owa.mailindex.0f9cc403.js:1:185190
st: 500
ehk: X-OWA-Error
efe: CH0PR04CA0033
ewsver: 15.20.9913.9
reqid: dd801cc5-0a7c-0c7b-ec95-afaa3f174e8b
cv: evrKU3VR3whDTJDdb4Ic/G.0.1.1

Answer 1

The error code in the log is an HTTP 500 “Internal Server Error” coming from Outlook on the web (OWA), combined with an AccessDeniedException in Exchange.

Key fields:

• BootResult: accessDenied and err: Microsoft.Exchange.Data.StoreObjects.AccessDeniedException indicate that access to the mailbox or data store is blocked/denied.
• st: 500 and Error: 500 show the server returned HTTP status 500.
• ehk: X-OWA-Error and et: ServerError confirm this is an OWA server-side error.

So, functionally, this means the OWA client tried to start up, the server returned a 500 Internal Server Error, and the underlying cause is that the Exchange data store denied access (tenant or mailbox access is blocked).

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References:

• OWA error reporting responds with a HTTP error 500 in OwaSerializationException
• Error Handling
• System Error Codes (500-999)
• Tried loggin into Teams and Outlook and got this message on outlook, and unable to log into teams. - Microsoft Q&A