I don't know. I guess the more isolation the better. Nobody reveals their exact spam filtering algorithms. My advice is purely based on guesswork (and by chance

I don't know. I guess the more isolation the better. Nobody reveals their exact spam filtering algorithms. My advice is purely based on guesswork (and by chance seeing people doing the "mark as spam" instead of the unsubscribe thing on their computers) Some years back I got most of personal mail sent from my server randomly rejected by Google. Dropping the blog newsletter was one of the things I did (the other was some fixes to my DKIM/DMARC setup that I think were suggested to me here on HN). I was sending the newsletter from a different server, but used the same DKIM domain and the same domain in From:. It was suggested to me that the newsletter could have been the cause for blacklisting. The newsletter was strictly opt-in through a form on my page and only had around 10-20 subscribers. It had a hard limit of at most 1 message per week. I think I was running it for around 3 years when I shut it down. Probably nobody knows what the true reason was, but some time after these changes I was able to send mail to @gmail.com domains again.