Step Two: Set up gmail to forward all emails to the new email account.
Step Three: Stop giving out your gmail address.
Step Four: Start marking all emails that get forwarded to you through gmail that you don't want to see as spam in gmail.
Step Five: Start migrating all real-life contacts and online accounts to use your tutanota email account.
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SERIOUSLY, start paying for email from an email-specialized company in some European country with extremely strict privacy (such as Germany). GET OUT OF GMAIL and OUT OF U.S.A. EMAIL-BASED PROVIDRES A.S.A.P.