I recently saw a case where two Shaw email addresses in the same household behaved differently.
One of them would simply not receive any email from a specific sender. The other one had no issues receiving emails from the same sender.
There were no error messages on either side, the email account was not full, and the lost messages were not in Trash or Spam. There were no settings on the problem account that would explain this behavior.
Even stranger, the emails in question never showed up on the problem account even after forwarding the same email from the successful account.
So, the problem account wasn't just rejecting the original sender - there was something in the message itself that caused it to get lost in transit.
Testing showed that the problem Shaw email account was rejecting a specific domain name in the text (i.e. "abcdefg.com").
That is, if the email - ANY email, from anyone - contained the phrase "abcdefg.com", it would be lost; otherwise, it was fine.
The successful account did not show this behavior.
From this, it IS possible for two different Shaw Webmail accounts to behave differently, and it IS possible for Shaw email accounts to silently reject and/or lose emails under certain specific circumstances.
I did not ask Shaw about this because (a) I don't care and (b) I doubt their tech support is equipped to understand / correct this issue. But it's definitely on the Shaw side.
It's not likely that anyone will actually run into this behavior. The domain in question (not actually abcdefg.com) is associated with a Chinese electrical equipment supplier. I read an unconfirmed report that they had a habit of spamming people, so perhaps they're on some kind of blacklist.
(And no, I have no idea why any such blacklist would be used on one Shaw account and not all the others. If you've got a better theory, I'd love to hear it.)
Regardless, I've been on Shaw for decades, and this is the first time I've personally encountered this behavior. So, not impossible, but (hopefully) extremely rare.
It is just barely possible that this has something to do with the Rogers transition. No way to know.