ProtonMail may not be the best choice if you're a stickler for standards. Their service unapologetically works only within ProtonMail. Send an e-mail to someone with a different provider and they get a link to a https view of the email.
They don't support PGP (Does Gmail?) at the moment, but are apparently working on it. What other approaches are there?
But you're free to use any client with GPG support – the beauty of open standards. There should also be browser plugins that add it to the web interface.
(JS crypto also has issues.)
Sort of, with a Chrome extension: https://security.googleblog.com/2014/06/making-end-to-end-en...
(I've never used it)
Is there another email provider that isn't hotmail, gmail or yahoo mail with good prospects at the moment?
I'm a paying Fastmail customer, and it's worth every cent.
But, I am having a hard time justifying switching my entire family over. A family of 4 is $20/mth, that's 25% of the cost of my internet connection and seems rather steep.
FastMail on the other hand is a closer equivalent to Google, supporting caldav and carddav for Calendars and Contacts; although as a downside you'll have to configure 3 accounts on iOS to get Mail/Contacts/Calendars via IMAP/CardDav/CalDav if I'm not mistaken.