Don't worry about me personally Lindi, thanks, we've determined it's a wide issue affecting many email service providers (and therefore many of us) which is suspected of being internet-policing blocklist (not blacklist) related.
This unavoidably happens at times to a few individuals / companies in our modern complicated society without them having done anything wrong, but something has to be done each time by the "victim", in this case the forum's response email address.
Details are in Email alerts not working
I'm sure @Admin are aware of it, perhaps it's a budget issue with what someone like Spamhaus may charge which I can understand the objection to. There's been many arguments on other security worldwide forums about that.
There are other possible solutions which I'm sure MC will be looking into.
Just my understanding of what is usually involved in this kind of problem, I may be wrong.
Sorry for the derailment of your thread Marsman.