Ride both horses at the same time for about a year. Setup Fastmail on a custom domain, forward your Gmail there, and as you see people emailing your Gmail, upda

Ride both horses at the same time for about a year. Setup Fastmail on a custom domain, forward your Gmail there, and as you see people emailing your Gmail, update those accounts as you get the chance. I had a Gmail as my primary for over 10 years, did exactly this for 3 years, and now I’ll get maybe 2-3 junk notices per year to my old Gmail.