I am unable to log in to my Outlook web account.

Good day @phạm nguyễn,

I hope you’re having a pleasant day and thank you for taking the time to post your question.

Based on the error you’re receiving, UserHasNoMailboxAndNoLicenseAssignedError (HTTP 500), this typically means that your Microsoft 365 / Exchange Online account does not currently have a mailbox provisioned and does not have a valid license assigned for Outlook or Exchange services.

In this situation, the issue is related to account configuration and licensing, which is handled at the administrator level. Since your post is tagged under Outlook on the web for business, it does appear that you’re using a work or organizational account. Unfortunately, if you’re an end user, you will require assistance from your Microsoft 365 administrator.

I’d recommend reaching out to your organization’s IT department and asking them to check the following on your behalf. They should confirm that your account has a Microsoft 365 license assigned that includes Exchange Online. If the license is missing or was recently changed, they can assign the appropriate license. In cases where a license is already present, but the mailbox wasn’t created correctly, removing and reassigning the license often helps refresh the mailbox provisioning process.

After the license is assigned or updated, it may take 1–2 hours (or up to 24 hours in some cases) for the mailbox to be fully provisioned. The admin can also verify that your mailbox exists by checking Recipients > Mailboxes in the Exchange Admin Center (EAC).

Additionally, since you’re accessing Outlook on the web, it may also help to clear your browser’s cache and cookies, or try signing in using a private or incognito window, as cached data can sometimes interfere with successful access.

Please note that this is a user‑to‑user support forum, so I don’t have access to your tenant or the tools required to make changes to accounts or licenses. That said, I do hope the guidance above helps point you in the right direction and makes it easier to resolve the issue with your IT team.

If you have any updates or follow‑up questions, feel free to leave a comment under this post. That will make it easier for me to receive notifications and continue supporting you where possible.

Thank you for taking the time, and I hope you’ll be able to access your Outlook account soon.

If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment". 

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.  

The error UserHasNoMailboxAndNoLicenseAssignedError (Error 500) indicates that the user account can sign in to Microsoft 365/Entra ID, but Exchange Online does not see an active mailbox or the required license for a mailbox.

Resolution steps for the Microsoft 365/Exchange Online admin:

1. Verify the mailbox status
   • In the Microsoft 365 admin center, open the affected user.
   • Check whether the user has an Exchange Online mailbox assigned.
   • If using Exchange Online PowerShell, check whether the mailbox is disabled or missing. If the mailbox is disabled (similar to AccountDisabled : True scenarios), Outlook on the web will fail to load.
2. Verify license assignment
   • In the Microsoft 365 admin center, confirm that the user has a license that includes Exchange Online.
   • If no such license is assigned, assign the appropriate license and wait for provisioning to complete, then try signing in to Outlook on the web again.
3. Re-enable or recreate the mailbox if needed
   • If the mailbox object is disabled or treated as terminated in Exchange Online, re-enable the mailbox for the user.
   • If the mailbox was never created or was removed, create a new mailbox by assigning the correct license and, if required, using Exchange admin tools to provision it.
4. Retry sign-in
   • After fixing license and mailbox status, sign out of all Microsoft sessions, clear the browser cache, or use an InPrivate/Incognito window, then try Outlook on the web again.

If not an admin, contact the organization’s Microsoft 365/Exchange Online administrator and provide the exact error: UserHasNoMailboxAndNoLicenseAssignedError (Error 500). The admin must check and correct the mailbox and license configuration as described above.

References:

• 403 Sorry Access denied error when a user tries to sign in to Outlook Web App in Microsoft 365
• Not able to have access to my email ! - Microsoft Q&A