Why are most "privacy" WebMail providers labelled as proprietary?
I was researching WebMail providers, and noticed that most WebMail providers recommended in privacy communities are labelled as proprietary by AlternativeTo.
I made a list of WebMail providers, private or not, to see which ones were actually open source:
Unless I'm missing something, it seems like people overlook this when deciding on WebMail providers. Is it a distinction between a proprietary backend server and a proprietary app, or is there a different way to decide if a WebMail provider is proprietary vs. open source? Lavabit was labelled proprietary by AlternativeTo, but open source by Wikipedia.
Note
If I have labelled an open source WebMail provider as proprietary by mistake, please provide evidence by linking to the source code, and I will happily change it.