As no native contact sync is supported on phones, at least an API is needed!

This would allow Linux desktop environments integrations. Sorely needed by open source communities.

The most helpful API would permit encrypted insertion or updating of data (XML or other structure) to a specific user's calendar and drive folder. The data could exist in a stack before validation/incorporation, or be automatically added if the sender has been previously authenticated.

Running our own secure mail service isn't necessitated since we have Proton.

The title is "Open API / Tools", so, it doesn't seem to be only for Proton Mail, and its associated Contacts.

I think this idea is also good for Proton Drive, which is the focus of this suggestion:

https://protonmail.uservoice.com/forums/932839-proton-drive/suggestions/43582125-protondrive-api

I think the best part of Open API's which each user must give permission, via OAuth2 or better, for another app to access is the community can create open source apps to fill in the gap of apps the Proton team hasn't yet had time to create.

I'd very much like the ability to create a folder in my Proton Drive for a specific use and then share only that folder with a third party document writer and spreadsheet creator app to save/retrieve/edit the files from that folder in my Proton Drive. As is, I must download the file, edit the file, then re-upload the file and delete the old one.

I'd certainly prefer the Proton team created and managed all the apps associated with their service (and their service would be worth even more $), but, that's a massive undertaking. Perhaps they could make forks of some open source apps and customize them to work with Proton's services. For example, LibreOffice.

This would be great. I'm evaluating suitable backends for a communication app and it's hard to find privacy minded options. A ProtonMail API would open up a world of possibilities.

Pourquoi ProtonAPI :
-- Pour l’émergence de clients plus à l’image de ProtonMail et des utilisateurs;
-- Pour intégrer ProtonMail dans plus de projets;
-- Pour promouvoir ProtonMail au près des développeurs.

Signé un libriste.

I, too, would like to see an API, which would be useful for a webapp I'm building. Any updates from the development team?

Even if this could be implemented/exposed in stages. Case in point, I have an elaborate sieve filter that I want to update. I'd really prefer to just be able to craft a command to add/remove lines to it (or update the entire rule, which I could maintain offline), but right now my only option is to copy/paste a file into an online form.

Same with adding contacts to my personal address book.

This is also essential functionality to any sort of email automation e.g. Firing a webhook upon receiving a certain subject line - but I understand how that has more sensitive and complex than just maintaining flat records of contacts and sieve rules.

Open the Protonmail API. I think it would be good if third part developers could implement their own client. It would be great if we were not bound to a single client.

would love this too! any reply from the team?

An api would allow me to integrate secure email on my portal.

Without a doubt this is the best secure email service I've encountered. Only the absence of an api keeps it from earning an editors pick on my site http://resistancejax.net16.net/

https://www.sendinc.com/ offer such an API

Yeeees, I would really like to see the API for ProtonMail.
It is the only thing that puts other email providers ahead from you. If you could only give us the API my dream will come true :D

I would also like this. I am evaluating ProtonMail. I like it, but an API would be very useful -- especially because it ProtonMail does not support IMAP or SMTP.

I would create a contact sync app with Google and iCloud

It would also allow people writing plugins for outlook, thunderbird, etc.

I would love to see a API, so to create free secure emails etc or maybe a way to upgrade to premium and set-up the domains etc.

I really like this idea. Open APIs would as Ugnius B suggested, make it possible for the community to develop additional functions or programs, even to additional platforms.

It should though be thought through thoroughly, if this could compromize security. If it doesn't, then please give us open API or even open source resources.

It also could allow to free you from the task of writing email clients and let the community do that.