Third party email services have an import feature and you can set up forwarding of all emails from Gmail to your new address. That alone allows you to make a m

Third party email services have an import feature and you can set up forwarding of all emails from Gmail to your new address. That alone allows you to make a move today (from my experience, it takes less than an hour), and then you can move your accounts as you go one by one. You'll probably get rid of a bunch of accounts in the process as well.