Unable to access my emails or teams calendar on my business account

Question

Unable to access my emails or teams calendar on my business account

Poppy Martin-Williams 0

I have tried clearing my browser's cache, cookies and history, and logging out everywhere using microsoft security, but it still comes up with this error:

UTC Date: 2026-10-16T12:51:07.862Z
Client Id: [Moderator note: personal identifiable Information removed]
Session Id: [Moderator note: personal identifiable Information removed]
Client Version: 20261008079.08
BootResult: configuration
Back Filled Errors: Unhandled Rejection: Error: 500:undefined|undefined:undefined
err: Microsoft.Exchange.Data.Storage.UserHasNoMailboxException
esrc: StartupData
et: ServerError
estack: Error: 500
    at Object.w [as createStatusErrorMessage] (https://res.public.onecdn.static.microsoft/owamail/hashed-v1/scripts/owa.mailindex.4997fccd.js:1:808)
    at https://res.public.onecdn.static.microsoft/owamail/hashed-v1/scripts/owa.mailindex.4997fccd.js:5:6626
st: 500
ehk: X-OWA-Error
efe: [Moderator note: personal identifiable Information removed]
ewsver: [Moderator note: personal identifiable Information removed]
reqid: [Moderator note: personal identifiable Information removed]
cv: [Moderator note: personal identifiable Information removed]

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Answer 1

Hello @Poppy Martin-Williams ,

Good day! I hope you're doing well.

The exception "Microsoft.Exchange.Data.Storage.UserHasNoMailboxException" typically means the user successfully signed in, but Exchange could not find a mailbox associated with the account. Outlook on the web starts loading and then fails because there is no mailbox available to open.

Firstly, could you please confirm whether your account still has an active license?

You can verify this by asking your Microsoft 265 admin to follow the following steps:

If you don't know who the Microsoft 365 admin is in your organization, you can find guidance here: How can I find my Microsoft 365 admin? - Microsoft Support

Sign in to Microsoft 365 Admin Center using admin credentials.
Go to Users > Active Users
Click on the affected username > Manage product license

User's image

Select Licenses and Apps
Expand Apps
Ensure that Exchange Online (Plan 1 or Plan 2) is selected

User's image

If the license is present, try unchecking it, reapplying it, and then allow some time for synchronization. This may help resolve the issue.

You may find this article helpful: Getting a mailbox not found error in Outlook on the web - Microsoft 365 admin | Microsoft Learn.

Additionally, please have your Microsoft 365 administrator verify if your mailbox exists for the user in Exchange Admin Center under Recipients > Mailboxes

User's image

If available, please ask your Microsoft 365 administrator to connect to Exchange Online PowerShell and run the following command: Get-EXOMailbox ******@domain.com

If the command returns the mailbox details, please share the output. If the command returns an error indicating that the object cannot be found, this would suggest that no Exchange Online mailbox is currently associated with the account, which may explain the behavior being observed.

For your reference: Get-EXOMailbox (ExchangePowerShell) | Microsoft Learn

If the issue persists, I recommend submitting a support request using an admin account: Get support - Microsoft 365 admin | Microsoft Learn

This is the most efficient way to escalate the issue, as support engineers have access to advanced tools and permissions to investigate further. The engineers in related team have higher permission and resources than me to help check the root cause from background directly.

I hope this suggestion helps. If you need any further assistance, please feel free to leave a comment.

Best Regards.