When comparing Google Inbox vs ProtonMail, the Slant community recommends Google Inbox for most people. In the question“What are the best e-mail clients for Android? ” Google Inbox is ranked 6th while ProtonMail is ranked 7th. The most important reason people chose Google Inbox is:
Inbox follows Google's Material Design guidelines, making for an intuitive and smart looking interface. Bold colors with clear text and intuitive actions allow for one of the better looking in house Google apps on Android.
Specs
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Pros

Pro Good-looking interface
Inbox follows Google's Material Design guidelines, making for an intuitive and smart looking interface. Bold colors with clear text and intuitive actions allow for one of the better looking in house Google apps on Android.
Pro Intelligent categorization
Inbox tries automatically bundling similar messages together. For example, Inbox will create bundles for travel information, receipts, promotions as well as group messages temporally. It enables also managing these bundles of messages together - they can all be swiped away together.
Pro Can snooze emails
It's possible to "hide" a message until a specific date and time or location, which gets the message out of your way until you're ready to deal with it. Swipe left and you can have the email disappear for a day, a week, a month, etc.

Pro Helps deal with messages quickly
Inbox has intuitive swipe gestures that allow quickly dealing with emails or groups of emails. It's possible to mark them done, archive them or snooze them for later by swiping. It allows you to keep inbox at zero messages easily.
Pro Surfaces important information from messages
If an email contains pictures, flight information, reservation at a restaurant, attachments, links, dates, phone numbers and other information that the application recognizes, it will surface that information in its main view. These items can be viewed and interacted with without having to open the message itself. It allows finding and taking action on the important email information quickly.
Pro Can add notes to emails
You are able to add notes or reminders to pinned items - very useful for long email chains when you can't remember what the main point was!
Pro Integrates Google Now reminders
For users of Google Now, Inbox integrates with the service allowing for reminders to be seen while using Google Now as well as set through the service.
Pro Integrates realtime updates in messages
Through a feature called Assists, Inbox offers context sensitive updates to messages. These include information such as flight status updates before a scheduled flight.
Pro Can create tasks from dates and tasks in messages
If a message includes a date, Inbox is capable of automatically creating a task from that information.
Pro Auto replies
Can reply to emails using an AI generated response
Pro Trips Bundle
Centralized "folder" for trip info such as airline, hotel, and rental car reservations. Similar to Google Trips.
Pro Categorizes mails by Bundles
In addition to the several automatic categories, you can also create your own bundles. Thus reduces clutter and enables you to archive a whole bunch of mails with one swipe.
Pro Built-in end-to-end encryption
Pro No personal information needed
To create an account you don't need to give any personal information, just choose username, domain, and password. Even the recovery email address is optional.
Pro Privacy respecting
User data is protected by strict privacy laws because all servers are located in Switzerland.
Pro Open Source
Pro Mobile apps
Apps for Android and iOS available.
Cons

Con Only supports Gmail accounts
No exchange email support or importing of any other e-mail services mail.
Con Will be shut down in March 2019
Con No rich-text (HTML) formatting for composing mails
Con No way to mark a message as unread once it's read
Con No way to delete a single message in a bundle
Con Javascript-intensive Webmail
Free accounts are required to use Javascript webmail and encryption is done in the browser. Javascript cryptography is harmful for security and should not be used.
Con Encryption Keys are stored server-side
The keys are generated during account creation. Using your existing keys is prohibited and ProtonMail must store and control the private keys. Encryption cannot be secure unless the user controls the private keys.
Con Still lacks some useful features
At the moment, there is no calendar feature and contact management is quite poor. They will, however, start to work on it.
Con Ties to US Investors
ProtonMail takes money from US Investors
Con No IMAP and SMTP support for basic accounts
Basic accounts are restricted to the Protonmail web client. Support for IMAP and SMTP is available with a paid subscription only, and as such with basic accounts it is not possible to send and receive email with external applications.
Con Overly expensive for desktop support
Con Requires phone number for login
If you sign up over Tor or a VPN, it will require email or phone number verification. Email verification is disabled if you use an email that isn't from Google or Outlook.
Con Not fully Open Source
