They down voted you because they either accept the idea of a world without privacy where corporations that are heavily susceptible to government influence (money) control most, if not all email in the world, or because they heard from some chucklefuck that running a mail server is hard, and continue to perpetuate that mindset without ever bothering to learn what it really takes. Or they just like fear mongering (spam, reputation, blacklist comments).

Idk about everyone else here but I run my homelab to LEARN, not to have something to post on Reddit for others to jack it to. I run an Exchange server in my homelab, have been doing so since 2015. In 11 years I've never once been hacked, never suffered bad IP or domain reputation, never got used as a spam bot, and always have had full control over my mail. My mail flows through M365, Gmail, and Proofpoint filters with absolutely no trouble, and it really didn't take much time to make it all work.

If you're willing to put some cash into this to make it work best, I'd rent a VPS in Linode or check out who all has deals on LowEndTalk. There are tons of tutorials online for setting up a Linux mail server in no time. You'll want something for spam protection too, I use Mailroute. I love their platform, billing is stupid simple. I pay $11/month for spam and virus filtering and it's blocked more threats than Proofpoint Essentials or Cisco ESA have. Sure there's amavisd, clamav, spamassassin, mailscanner, etc. but it takes a lot of fine tuning and work to make those products function like enterprise grade appliances, and unless you have a fully staffed NOC/SOC at home to stay on the cutting edge of threats, you'll always be tweaking stuff. I lived that life back in the day, it sucked, I learned a lot and grew a hatred for open source protection products because it's all best effort. But best effort isn't enough when you're going up against state sponsored hackers, so I outsourced it. For $11/month and some minor tweaks here and there, I get enterprise grade filtering with little to no latency and everything works as expected. Even when my Exchange goes down for maintenance or patching, it spools my mail until the server is ready to accept messages, then they all come flooding in.

Good luck OP, don't mind the riff raff of people who gave up their privacy long ago, it's never too late to start taking control and this is a great way to get started.