said by kevinds:Shaw's open relay servers, can not verify if the emails are From who the emails say they are, so disabling NDR's is the right thing to do.
Because shaw disables NDRs, it makes troubleshooting 10x harder when email issues arise.
I don't know of any other ISPs that disable NDRs but shaw. Telus doesn't disable NDRs and when email issues arise, troubleshooting is much more streamlined.