I’ve moved my mail, calendars and contacts off Proton. The main reason is that I didn’t want a subscription anymore. That alone rules out every hosted provider with a custom domain. I also wanted real IMAP (instead of Proton Bridge), calendars that sync on Arch and GrapheneOS, and wanted to keep the ability to invite people to events and answer invitations from my mail clients. Stalwart does all of that in one binary, so it went into the cluster.