I cannot vouch for this because I literally just found it two posts down after reading this one, but the developer of the JellyBox music player has a relay plugin for Jellyfin. It seems to specifically exist for the music player, but that’s still useful for some people: https://github.com/JellyBoxPlayer/jellyfin-relay

I run Stalwart for the server, Bulwark for the webmail frontend (using JMAP), and SMTP2GO for outgoing mail (free tier is more than enough).

I selfhost Stalwart for incoming mail with the free SMTP2GO tier for outgoing mail. This is for my personal email that I currently don’t use for anything. I use gmail for signing up for stuff because I’ve been using it for a very long time and haven’t picked an alternative setup yet for handling signing up to stuff with a different email. I also use Zoho mail for more important things like banking. Zoho makes its money from enterprise subscriptions and I frankly trust it more than Proton to not enshittify short or long term.