ehh... it's been known for awhile that protonmail is in the pockets of the US government so it's not really a loss for the russian people.

What they should be using is either Streisand[0] email with a server in a country that respects their privacy(neitherlands, panama, etc) or lavabit email[1].

[0]: https://github.com/StreisandEffect/streisand [1]: https://lavabit.com/

EDIT --

Sorry streisand doesn't in fact have an e-mail server. I thought it did at one point. I guess you can use mail-in-a-box(https://github.com/mail-in-a-box/mailinabox).