If your concern is being blocked, the best advice is to avoid any free email service and pony up for a paid one.

ProtonMail used to be the big one, but IIRC they had some controversy recently:

https://cointelegraph.com/magazine/proton-mail-exposing-activists-info-showed-the-limits-of-encryption/

https://discuss.privacyguides.net/t/the-intercept-proton-mail-says-it-s-politically-neutral-while-praising-republican-party/24456

Other commenter already mentioned Zoho, but also mailbox.org.