@rysiek
Just noticed your original post. A good option for lowtech users used to be #Hushmail since non-HM users could do all the key management. Now that HM has a cost that I usually can't impose on others, I often pimp #ElectronMail (& thus #Protonmail). It's worse than HM but it's a sad state of affairs these days. Anything else becomes too challenging for normies.