A few weeks ago, Google began rolling out a new Highlights feature for Inbox that promises to bring your most important email to the top of the list. Many people still don't have it, so this may only be available to a small group for initial testing, or perhaps the rollout is just progressing very slowly. A teardown of the latest update to Inbox includes signs that there is a new training tool that will be useful for making Highlights even better.
The features discussed below are probably not live yet, or may only be live for a small percentage of users. Unless stated otherwise, don't expect to see these features if you install the apk.
New text in the Inbox update encourages users to "train Highlights" to make it better. The basic idea is not unlike what Gmail and Inbox have already been doing for ages by observing patterns of how you read, reply, and otherwise interact with email, then use that data to give more prominence to the messages that are likely to be important to you.
The difference in the new training tool is that you're meant to take an active role. There will be a line in the Settings screen for each account that opens up a new screen to begin the process. It's a bit reminiscent to the 'improve your recommendations' tool in Play Music, but instead of asking about genres and bands, Inbox will display some of your email and ask you if similar emails should be highlighted in the future.
<string name="bt_highlights_training_setting_title">Train Highlights</string>
<string name="bt_highlights_training_done_page_title">Nice job!</string>
<string name="bt_highlights_training_done_page_subtitle">Training makes Highlights better. Train more anytime in Settings.</string>
<string name="bt_highlights_training_content_page_title">Was this a Highlight?</string>
<string name="bt_highlights_training_content_page_subtitle">Train Inbox whether to highlight similar emails in the future.</string>
<string name="bt_highlights_training_content_page_skip">Skip this email</string>
<string name="bt_highlights_training_no_data_title">No emails available for training</string>
<string name="bt_highlights_training_no_data_subtitle">There are no emails available to classify right now. Try again later!</string>
<Preference android:enabled="true" android:title="@string/bt_highlights_training_setting_title" android:selectable="true" android:orderingFromXml="true" android:key="@string/bt_preferences_ash_htt_settings_key" />
<activity android:name="com.google.android.apps.bigtop.highlights.HighlightsTrainingActivity" android:exported="false" android:screenOrientation="portrait" android:theme="@style/bt_BigTopAppTheme.NoTitle.HighlightsTrainingActivity" />
Highlights is only appearing for me on a single account on a single device (weird, right?), but the training tool doesn't appear with it. I doubt it's live yet, but keep watch for it because it may go live before the next update.
The APK is signed by Google and upgrades your existing app. The cryptographic signature guarantees that the file is safe to install and was not tampered with in any way. Rather than wait for Google to push this download to your devices, which can take days, download and install it just like any other APK.