I use Fastmail instead of ProtonMail, but the premise from my understanding from talking with others is the same.
Protonmail has an import feature that works extremely well when migration from Gmail, and from there you would forward any mail from Gmail to your custom domain. Whole thing takes maybe 10-15 minutes.
Protonmail has an import feature that works extremely well when migration from Gmail, and from there you would forward any mail from Gmail to your custom domain. Whole thing takes maybe 10-15 minutes.
Your mileage may vary slightly however.