Alarig Le Lay:

But for MS, it’s impossible. I’m a the point where I stopped trying, I’m
just not reaching them whatever I do. So when I have to write to someone
hosted by them, I ask for a different email address.

The ironic thing is that every non-spambot that gets rejected by me for not following the RFC rules - eg by not trying again when my end says 'not at the moment, try again' - runs MS Exchange.

Ian