we can argue all day long about why this happens. more interesting for me would be, what can i do about it.

i have noticed the same problem. since a few weeks, i can no longer reach gmail from my mail-server.

my mail volume is to small that marking mails non-spam would help. besides i nowadays mainly use email for situations where i don't have an alternative way to communicate, so when i email someone, and it gets rejected, there is no backchannel to let the recipient know about that.

reading through that thread, one solution suggests itself: don't host your email server with a provider that tolerates spammers.

does anyone have recommendations?

where can i host my own mailserver, and not suffer from being stuck in an IP block that is on any blacklists?

are there other solutions?

can i use a reputable mailserver as a proxy? so that mail gets forwarded to my own server, and mail i send out gets sent through them, but i still do all the filtering, routing, management of email addresses, storage, etc, of emails on my own server?

i know this is technically possible but which servers out there support that?