Hello, This is the 3rd day that suddenly the emails from my sister are not getting through to me.

They are being returned to her with this message.

This message was created automatically by the mail system (ecelerity).

A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:

>>> XXXXX@shaw.ca (after MAIL FROM): 550 5.1.0 <XXXXX@mymts.net> sender rejected AUP#CDRBL

Neither of us has changed anything in our emails recently.

She is with MTS and it seems that now when she sends an email to anyone with a Shaw email, it is rejected.

How do we fix this?

Thanks