I've been very happy with Protonmail, you can even use your old Gmail address from within Protonmail [0]. Although arguable doing that is counter productive, you want receive gmails but reply with you new address -> Yes this is the time to buy a domain and own an address for the rest of your life, so you can move again with little pain in the future ;)
[0] https://proton.me/blog/proton-mail-connect-gmail