Fedi doesn’t support secure communication, that’s why (the last time I dove into the subject) lemmy has a profile field for yer Matrix account. Encrypted communication. Mails are usually hosted on “reputable” services and has some sort of privacy agreement, something I’ve yet to see on a fedi site.

And if you think of lemmy or mastodon as a communication service rather than a publishing platform, you’re probably being spied on more than you expect.

Fedi logins would require an account backend, which is quite a way aways from the fediverse as far as I know. Not to mention it would require a stable, permanent fedi provider with absolute trust.

For a simple e-mail server you could use a server management suite like YunoHost, comes with a working mail server right out of the box. For only recieving registration mails and notification you wouldn’t even have to mess with online spam filters due to not being GAFAM.

Someone mentioned UnifiedPUSH, which is nice but has very limited platform support at the moment as it has to be added to every single site and app. As far as I know it also sends notifications only using transport encryption so the server admin would have access to your notifications. Better to self-host, best to self-host at home on your own hardware.