@cancel @aral Yeah. I did actually run my own for a while but I used the free tier of a well-known mail service as a relay, which mostly solved my blacklisting problems.

The real PITA, to be honest, was the lack of resilience of a Rasberry PI on the end of a broadband line (which was what I was using). It didn't happen often but when it did break it was (of course) always when I urgently needed it!