It doesn’t matter to Google that I have DMARC, DKIM, and SPF records that practically guarantee the mail server is legitimate. The domain isn’t blacklisted and I don’t send bulk mail. But ever since the IP address changed, for the past six months all my messages have been marked as spam in Gmail (so for almost everybody).

There’s zero recourse. You simply don’t matter when it comes to the big players, and it sucks when it happens to you.