no storage for free plans & no storage plans
Criptext which is a privacy focused email provider is based on not storing emails. How it works is that they have a desktop and mobile clients. These clients are required to use Criptext and you have no cloud storage for emails. All of your emails before you recieve them in the Criptext clients are encrypted and in limbo on Criptexts servers and if you do not retrieve them with a Criptext client after X months, the emails are deleted.
I would like to see ProtonMail have this as an option. For free ProtonMail accounts you will get no cloud storage. Then there could be free plans which have no storage but all the other benefits a Plus and Visionary plan include like email aliases, encrypted contacts, etc.
The reason I like ProtonMail to have this as an option over using Criptext is that ProtonMail is based in Switzerland and the servers which store all the ProtonMail accounts are in a bunker which is much more secure than Criptexts servers physical infrastructure.