InstAddr VS NeutronMail

I'd recommend https://m.kuku.lu/ for e-mails. You can choose your own username, password and also use 2FA and don't need to enter any additional information. I also use it for school mail. Source: about 1 year ago

You can get a .jp address at https://m.kuku.lu/. Source: over 2 years ago

InstAddr for temp email without losing the email account. You choose when to delete it. Source: almost 3 years ago

PS: I hope that we selfhosters will have a modern, efficient, easy to use mail suite one day with modern features like JMAP, good self-learning spam integration, automated checks and validations for SPF/DMARC/DKIM or whether the IP/host suddenly appears in a blocklist and integrated encryption at rest for emails. Something that isn't 30 services in a container image, with 30 different configuration styles. Maybe... Source: about 1 year ago

A bit related: there was a FOSS backend once but I don't think anyone wants to push further. Source: over 1 year ago

Some folks once started neutron which is an email server that can be used with the FOSS Protonmail web client but it was abandoned. And I guess you'd want to support JMAP in addition to IMAP as well apart from having automated encryption of incoming plain-text emails. Source: over 1 year ago

Anyway, to the topic: there was once neutron which is a server that aimed at ProtonMail compatibility. So that'd would simply would be able to use the same open source frontend from ProtonMail. However, this was abandoned. So you, or somebody else, could revive it. Source: almost 2 years ago

Some folks also started implementing an FOSS ProtonMail but this project was abandoned at some point. But maybe someone will fork and revive it one day. Source: almost 2 years ago