Unable to send or receive email with and without attachment

For a Microsoft 365 business account, this combination of symptoms points to either a mailbox/license problem or an Outlook client/profile issue.

Try these in order:

1. Verify the mailbox works in Outlook on the web
   • Sign in to the Microsoft 365 email account in a browser.
   • If email also fails there, the issue is not just the desktop app.
2. Check whether the mailbox or Microsoft cloud storage is full
   • If Microsoft cloud storage is full, email cannot be sent or received.
   • Check mailbox storage and remove large items if needed.
   • Messages sent to the mailbox while storage was full can be bounced back and unrecoverable.
3. Confirm the account is not blocked and the password is current
   • If the password was changed recently, update it.
   • The account can also be temporarily blocked because of unusual sign-in activity.
4. Check for common send blockers
   • Messages with attachments larger than 25 MB cannot be sent in Outlook.com.
   • If a message is stuck because of a signature-related error, remove the signature and resend.
   • If a non-delivery report is returned, review the reason in that report.
5. Update Outlook and Windows
   • Out-of-date Outlook or Windows can prevent sending and receiving mail.
   • Run Windows Update.
   • In an Office app, go to File > Office Account or Account and use Update Options > Update Now.
   • For Outlook for Microsoft 365, version 2008 (Build 13127.20508) or later resolves a known metered connection send/receive issue.
6. Run Microsoft troubleshooting tools
   • Use the Support and Recovery Assistant for Microsoft 365 to diagnose common Outlook connectivity issues.
   • If using classic Outlook, Microsoft also provides classic Outlook troubleshooters.
7. If Outlook desktop shows the wrong account type
   • Since the desktop app is showing a free email account while the subscription is Microsoft 365, test in the browser first.
   • If the browser also cannot send or receive, this points away from a local Outlook app problem and toward the mailbox or tenant side.
   • In a business tenant, an admin should verify that the account has an active Exchange Online license assigned. A user account can exist without an active Exchange mailbox.
8. If multiple users are affected
   • An admin should check Microsoft 365 Service health status for Exchange Online.
9. If support cannot be reached through normal channels
   • In Outlook.com, use Help on the menu bar, enter the issue, then go to Still need help? and select Yes.
   • For Microsoft 365 business products, use Contact support for business products - Admin Help.

If Outlook on the web fails and the Exchange Online license is missing or not applied correctly, mail will not send or receive until that mailbox issue is fixed.

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