You know you are onto something when users are begging you to let them give you money and are even concerned about your monetization strategy. Savvy app users have been burned by too many app sunsets. Spark, the great new email app from Readdle, had so many users asking they decided to write a blog post about it. It's interesting what they are trying to do and shows the 'outside the box' thinking needed in today's app market to build a business instead of just an app.
Sidenote: Ever since the demise of the Mailbox app, I have been searching for a worthy replacement. The day Spark's macOS client was released, I jumped on board to try it out and haven't looked back. If you loved Mailbox, give Spark a try. I love it.
A few words about Spark’s business model by Alex Tyagulsky