The Gmail Android app will warn users when have opened a potential phishing website. The feature is rolled out gradually, according to Google it can take several days before it become available for everyone.
The app scans for potentially suspicious links in emails. If the user clicks such a suspicious link, a warning is shown before the page is opened.
It's not entirely clear how the technology works, but likely Google uses its Safebrowsing database with malcious websites to determine whether the email links to a malcious page.
It's unknown when and if the feature becomes available for the iOS version of the Gmail app.
