Hi! Superco. Thanks for the details and for bringing this up, I'm here to help.
The “message failed to send” issue in Microsoft Teams can happen for a few different reasons, and the fact that all of your messages fail points to either an account, license, or network/policy issue.
Here are the possible fixes to the issue:
- Check if you can message teammates in your own org
- If you can chat internally but not with external people, this is a policy/permission issue.
- If you cannot chat with anyone at all, it’s likely account/license or suspension.
- Sign out and clear Teams cache
- Quit Teams.
- Delete the cache folder:
- Windows: C:\Users<YourName>\AppData\Roaming\Microsoft\Teams
- Mac: ~/Library/Application Support/Microsoft/Teams
- Restart Teams and sign back in.
- Test Teams on another device / web version
- Go to https://teams.microsoft.com and try sending a message.
- If it works there, your desktop app is the issue.
- Check with your IT admin (if using work/school account)
- Ask if external messaging is allowed.
- Verify your license is valid (e.g., Microsoft 365 Business Standard, E3, etc.).
- If using Teams Free (personal)
- External business accounts often won’t accept messages from personal/free Teams accounts.
- In that case, you’d need the recipient’s org to enable “External Access.”
- If you think you’ve been blocked for spam-like behavior
- Stop sending repeated identical messages.
- Wait a few hours or a day, temporary restrictions sometimes lift automatically.
See if this helps. If you need further assistance, just let me know.
Best regards,
Kimberly