Sure the client is open source,
server code is closed source.

So if proton enshittifies or ceizes to exist,
the open source clients will be useless,
since you or someone else can’t host the server, since that is closed source.

But whatever man, good for you if you like them and want to remain oblivious of the risks! c:

No, I mean their email server + protocol.
The thing you’d use to self-host a proton mail email server.

What you linked is the source to the client,
which interacts with the proprietary server code to fetch your mail from them.

If you can’t self-host / switch to a different server if they enshittify due to being closed source, then it’s not “open source” nor “portable”

Then please do link me the source code of their email protocol.

FairEmail’s FAQ is the 1st thing that popped up on Github when searching for “proton”, mentioning that it’s proprietary:
https://github.com/M66B/FairEmail/blob/master/FAQ.md#faq129

2 words I want you to keep in mind:

• Entranchment
• Enshittification

I purposely do not use the whole Proton suite for those reasons. It would be quite bad if one is entranched by their whole suite if they went on the enshittification route, which large companies eventually tend to do.

It’s a game where you push in the teeth of the alligator, with a chance that it will bite you.

It’s been since my childhood since I’ve played it, but if I remember correctly, the goal is to push in as many teeth without the alligator triggering, and of course if it triggers, to try to pull your fingers out before you get clamped :P

It can hurt a bit if you get clamped, but it’s not strong enough to do any real damage to your finger.

I hate that nowadays everything comes with pre-installed spyware and that they charge you for it makes it even worse…

• Want a TV? Suck on our Android TV with Google spyware embedded
• Want a phone? Get our Android with Google spyware, or go for an Apple with Apple spyware
• Want a computer? We’ll shove Windows spyware down your throat

Ffs I just want devices that I own to not spy on me, and I can’t even buy them anymore…

Each of them require flashing a custom privacy respecting OS onto it,
and that’s a real problem…