I recently signed up with the Protonmail. And like zoho they too have multiple apps and they are allowing the proton drive for hosting the files. And those files can be stored through cloud and additional file in the free account can be added as well. 

When you sign up to the Protonmail you would be getting the free account with 2GB storage benefit. And more you can add with premium plans. And you can get the bonus if you follow the steps. 

Now more steps you would be completing you would get the 3GB additional bonus for the same. You should follow those steps and that would get your enough space for the cloud storage. You can check the below image for the steps. 

As you can see this is a good offer. You would be able to add the space for the drive. And considering this is mapped to the single protoonmail account, one place for all the services is a good thing. I also think that the services and the offers like these would be super good for the usage as well. I like how the protonmail add such service for the hosting of some assets. 

3GB and 2GB in the era of where the images and videos are consumed like paper is a not big offer. But it is better than nothing. As with time such type of the offers would only get things in a difficult order as well. 

Are you using the Proton drive or any of the protommail services? What part of those services you like? Any specific features or the set you would like to share?