So, the fine folks at SORBS DUHL decided to add a range of IP addresses to their e-mail blacklist, perhaps having something to do with Chinese misbehaviour, it's a bit difficult to tell. My wife's second e-mail address DNS server just happens to fall into that IP range so by default it gets onto the blacklist. It took a while to find out that people could no longer send her e-mail as some were slipping past the block and some that were blocked were not sending bounce messages. I suspect that some of her correspondence did not recognize the importance of the bounce messages to troubleshooting, so we did not hear of them.
I did an on line chat with Shaw tech support and ultimately received a placation of "there's nothing wrong on our end."
I was able to verify the problem and the bounce messages indicated that Shaw's mail server was the source of the rejection.
Back to Shaw. The answers ranged from there is no problem, to it's on the e-mail blacklist, our servers are not blocking it, our servers are blocking it and finally settled on you will just have to wait until the blacklist block is removed. Not the answer you want to hear for your e-mail. That after about 3 hours on chat.
I also had trouble with e-mail generated by two Drupal 7 based web sites hosted by Shaw Business. Messages were not being delivered to gmail and yahoo mail addresses. Despite numerous attempts to resolve this, efforts were unsuccessful and I moved both sites to a different host.
My bottom line? If your Shaw e-mail works, enjoy it. If it doesn't, don't expect anything more than a monthly bill for service and a runaround from tech support.