Windows Live Mail Can receive but not send “This Message was undeliverable due to the following reason:”

OT:Windows Live Mail    Can receive but not send.

Hi

Dell XPS 1645, Windows 7 Premium 64, Windows Mail Live, Defender Anti Virus, Malwarebytes Anti-Malware, Bell Sympatico Fibe.    eMails are returned with the following message each and every time :

This Message was undeliverable due to the following reason:

Each of the
following recipients was rejected by a remote mail server.
The reasons given
by the server are included to help you determine why
each recipient was
rejected.

554 mailgate.mmic.net

     <recipient>

Please
reply to <*** Email address is removed for privacy ***>
if you feel
this message to be in error.

Tried eMail with attachment, without attachment, with CC and BCC, without CC or BCC, with receipt request, without request...all fail.    eMailing another computer in my house is successful.

Uninstalled Windows Live and reinstalled it.    This did not help.    I changed the name of the account.    This did not help.

Removed malware and defender.    Tried again.    Same issue.    msconfig, unticked everything but Microsoft services.    This did not resolve the issue.

If I log in at Bell.net, log in and use Outlook, everything works fine.    I want to use Windows Live Mail as I have been for the past 6 years.

Assistance would be appreciated.

Thank you

Paul