If Google's spam filters block an IP or subnet that happens to be where you host your self-hosted mail server, it will be almost impossible for your mail server reputation to ever recover. Your emails to gmail users (a vast percentage of all email users in many places) will never be delivered and maintaining your own mail server will become a nightmare.
Google has very good spam filtering, but their lack of human controls or support make it impossible for the little guy to get resolution in many cases where a spam score may be undeserved.
I've been hosting my own mail server since 1997, at its current colo since 2007 or so. I've never had any issues with delivering email to gmail users.
So, I'm curious, am I just extremely lucky to have competent sysadmins as neighbours on the colo subnet, or is my IP address' reputation so good that it never gets affected by collateral damage?
Me too, for almost as long. Never a problem with gmail, although I do suppose that's partly luck. If my IP block ever got blacklisted, I would move the mail server to another IP - I'm sure that would be easier than trying to reason with Google. I do get a bounce from Hotmail every couple of years, but my attitude has become "your fault for using Hotmail".
