German hoster united internet. The few people I know with those addresses receive a signal message.

That worked like a charm for me, but some strange German mall hoster demanded the blood of an unborn unicorn or something like that for it to work.

I managed to get my mails through 95% of servers I’ve tried, and after evaluating the 5% that didn’t accept my mail, I just realized they can suck my man-tits. But maybe those 5% in your case might be recipients you value.

I’m poking my eyes out just to be safe