I agree that there may be earlier filtering stages, though in my experience even if you send unauthenticated messages from not-really-configured postfix on Ubun

I agree that there may be earlier filtering stages, though in my experience even if you send unauthenticated messages from not-really-configured postfix on Ubuntu they would still be viewable in recipient’s spam, or at least that was the case a few years back. I’m pretty sure recruiters’ emails peterwwillis mentioned would not be as bad as to be eliminated before spam folder.