Next, scroll down to the Data Usage section and tap Manage labels.
Select a label, tap Sync messages, then pick an option: None, Last 30 days (or another period of time; more on that in a moment), or All.
Bonus tip: The more labels you sync, the more mobile data you'll use, so you may want to sync your Gmail labels sparingly.
Get notifications for the Gmail labels you choose (Android)
Now your Gmail app is syncing some of your labels, how about getting a notification whenever a new message with that label hits your account? That could come in handy if you've got Gmail filters that automatically label messages as they arrive, bypassing your inbox as a result.
Go back to the Manage labels setting. Tap the menu button at the top of your inbox, scroll down, tap Settings, select an account, tap Manage labels, then pick a label that you're syncing.
Check the Label notifications box, then choose an alert tone, toggle vibrations on or off, and decide whether you want a notification for each new message with a given label.
Decide how many messages you'd like to sync (Android)
Back when we were learning how to sync messages with certain Gmail labels, one option was how many days of messages you'd like the Gmail app to sync: none, a specific number, or all.
You can decide how many messages you'd like Gmail to sync for your inbox and other specified labels--anywhere from one to a hundred or more. (Again, the more old messages you sync, the more mobile data you'll use.)
Tap the menu button in the top-left corner of your Gmail inbox, scroll down and tap Settings, then tap an account.
Tap Days of mail to sync and make a selection.
Swipe between message threads (Android, iOS)
Here's a handy little Gmail feature that's easy to miss. Want to read the next message thread in your inbox? No need to tap the Back button to return to the inbox screen. Instead, just swipe from right to left (for older threads) or left to right (for more recent threads).
Attach big Google Drive files to your messages (Android, iOS)
With a little help from Google Drive, you can send a massive file--as in, say, more than a few GB--to a friend via email, or deliver a large batch of files.
Don't have a Google Drive account? Well, if you're using Gmail, you've actually got one already.
First, you'll need to load the files you want to send into Google Drive. Open your Google Drive account, then drag the file you want to send onto the web page. The file should begin uploading automatically.
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