Inbox Sunset as of March 2019
Google has a proud history of killing off the best email applications.
Take Sparrow as an example. Its innovative approach to email set the trend for the design of email for years to come. They killed it off July 20, 2012.
Back then I wrote that it was a sin to kill a Sparrow. Sparrow was loved by its users and Google swallowed up the team without offering users an alternative.
In that tradition today Google announced that Inbox is being discontinued and will cease to function as of March, 2019. Similarly they have not incorporated the features of Inbox into the new Gmail.
Disappointing but not surprising given their track record.