A few Inbox features that have not come to Gmail includes bundles that group emails jointly into a single one, and GitHub/Trello notifications. Inbox was opened to the public in 2015, just a year after Gmail was introduced as an invite-only.
Inbox came as an experimental tool in 2015 with features like newsletter previewing, accumulating emails from an event, and an unsubscribe card for unclicked emails during a period. The email was preferred by a small number of supporters who experienced rare-updates. Users remained comfortable with Gmail experience rather than Inbox.
According to the Google Play store, Gmail app has been downloaded by more than 1 billion times while the Inbox app had just 10 million-plus downloads. According to Statista, Gmail stands second at 27% in the most used email clients as of June 2018, following Apple (AAPL) iPhone email client.
In 2015, 232.8 million internet users sent the email at least once a month and this is predicted to grow to 251.8 million a month in 2019, according to Statista. On the other hand, global email users amounted to 3.7 billion in 2017 and this is likely to climb to 4.3 billion users in 2022.
After Inbox, Google has accumulated enough knowledge on how to make email better. The company has devised a transition guide for Inbox users to switch to Gmail. Google has stressed that Inbox users should familiarize with the new and updated Gmail interface as both of them work with the same email address and data.
Invariably, Google developers were using Inbox as a testing tool for improvising Gmail. The company has combined its resources and turned their focus to the familiar email service rather than Inbox. With the increase in email sending users, Google is depending heavily on the revamped Gmail.