Tuta Mail: Create a secure, private & encrypted email account for free
www.tuta.com
Tuta is the secure email service, built in Germany. Use encrypted emails on all devices with our open source email client, mobile apps & desktop clients.

What other free options are out there? Proton Mail’s free plan restricts to only 3 folders.

EDIT: After careful discussion with others, I’ve reluctantly decided to stick to Gmail, because we don’t know if these other providers will still be around 50 years from now.