I love your name, coincidentally the app mentioned here is called April - its voice only.

But for email companies - Superhuman is the most successful one.

Other solution which provide different features include Airmail, Sanebox, Mail0 to new a few - we feel this space need a bit of disruption as there is too much noise in emails while being one of the most important tool - we are trying by going voice first - will learn and implement based how it goes.