Running own SMTP server for personal use is hard. Google is the worst adversary just because of their market share. I have a mail server for personal use, and

Running own SMTP server for personal use is hard. Google is the worst adversary just because of their market share. I have a mail server for personal use, and I send less than 10 mails per day for many years. DKIM, SPF, DMARC are all properly set up. I am signed up to all possible postmaster tools, including that of Google. Still, Google started blocking mail sent from my IPv6 address in December. I switched to IPv4, and it fixed the issues for existing gmail recipients, but new recipients usually see my mail in Spam. When I don't get a reply for a few days, I mail them from my backup @gmail.com account and ask to unmark me as spam and add to contacts. So far, this helps. P.S. I also run a community website on a different domain and IP. It sends tens of thousands of notification emails per month, and it fares better in Google Postmaster Tools. User-reported spam is within 1% and it seems that this is acceptable behaviour for Google.