July 2, 2021
According to Google, users of the Gmail iOS mobile app must upgrade to the latest version before July 7, 2021, to avoid service disruption. Google has discovered an issue with previous versions that could result in the application hanging, crashing, or going into unusual application states.
If you do not upgrade to the latest version before July 7, you will receive an in-app prompt requiring you to upgrade to the latest version.
You can download the latest version of the Gmail iOS app from the Apple App Store.