Comment by stonesweep

Two domains registered at two different places, then cross-connect them at the registrars. To keep it fully distributed, you'll want to host one domain at one provider and the other one at a second one. (I do this - it's ~$10 USD/mo for both providers email hosting and ~$10/year to register each email domain, usually big discounts if you purchase for many years at once)

A second hosted email domain has an additional benefit - it allows you to also control your recovery (secondary) email, such as you'd add to your banking/financial website, etc. and not have any of your email options where they can be taken away like this post. It's trivial to have one of the email hosted providers do an IMAP pull from your GMail account, so you can still keep it around just manage it as an external account (such as for your Android login needs).