When using windows mail you cannot send or receive because you get an error. Windows Mail Error: "-ERR invalid command".
This error is caused by a setting in Windows Mail.
- Go to Tools.
- Click on Properties for the account you are having issues with.
- Click on the Servers tab.
- Uncheck the box, Log on using secure password authentication.
- Click Apply.
- Click OK.
- Try to send and receive mail, it should work correctly.