In any case, i don't like put only one star but ..
Protonmail is the dumbest email service in the world
If two people access their email from the same IP address, both email address are automatically blocked and unusable.
You might say that's impossible, but yes, they're that stupid.
Not creating multiple email addresses from the same IP address would have been a good idea, but not allowing two different people to connect via the same IP address? You have to be seriously delusional, and profoundly so, if I may add.
How can such nonsensical behavior be used in a business ?
Some people at ProtonMail should be fired.
Claim your business profile now and gain access to all features and respond to customer reviews.