Google talk about this shut down in 2018. In September 2018 Google announced that Google inbox will be shut down in March 2019 but Google inbox is still working right now.
Now when you open the app it displays that Google inbox will be shut down after 14 days or on April 2, 2019. Which is disheartening for people who daily use the Google inbox. Well it is now official and Google will shut down the Google inbox on April 2, 2019
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