This is pretty much exactly the reason I stopped running my own mail. I had the mail host on a static IP, part of a block of "pristine" IPs from a local colocation operation (iNOC in Albany, NY). Ran fine for years, but I started having to call more and more customers about "why haven't you answered my email from two weeks ago?" only to find out I ended up in the spam bin. Wasn't worth it when the risk was losing business.

I moved to Proton Mail as I like their simple interface and support their goals. Pretty good service so far, worth paying for, but I do sort of miss running my own services.

If you run your own mail server in 2022, you are the resistance.