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.

1. Go to Tools.
2. Accounts.
3. Click on Properties for the account you are having issues with.
4. Click on the Servers tab.
5. Uncheck the box, Log on using secure password authentication.
6. Click Apply.
7. Click OK.
8. Try to send and receive mail, it should work correctly.