«So, starting today, the MX records of my personal domain no longer point to the IP of my personal server. They now point to one of the Big Email Providers.» I

«So, starting today, the MX records of my personal domain no longer point to the IP of my personal server. They now point to one of the Big Email Providers.» I would have kept the MX records pointing to my personal server, and I would have changed only my configuration to send outgoing email through a third-party relay (eg. Gandi). This would have solved all the author's problems (deliverability issues) while staying 99% self-hosted.