5 stars: ProtonMail is great. I've suggested it to a number of friends and upgraded to the paid version. It's secure with a reliable clean layout. The mobile app works seamlessly. The singular downside I've found from switching away from Gmail is that the inbox search feature is not as good. It's fine for searching names/emails but not so much for emails containing key phrases or words specifically.
4 stars: Overall works well and looks good. Missing features. Needs to combine multiple emails into a conversation like desktop does. Needs the ability to add and delete filters. Would like the ability to swipe to go back and forward when in an email to go to the next email. Would prefer to see folders and labels in two seperate lists, similar to desktop.
4 stars: Love the app and being a member of the ProtonMail community. My only problem with the app and mail in general is when you're searching for messages with attachments, ALL types of attachments are included, such as email signatures in jpg or png formats instead of documents. Would be really nice to be able to filter out those types of attachments from searches because it becomes quite frustrating to be able to find what you're looking for!
3 stars: I love the product but the syncing functionality of the Android app is lacking. Push notifications and the app state do not stay in sync with the web client: the notifications tell me I have unread messages that I've read on web and the app does not update state in t...