Google has announced in a blog post that Gmail will stop working on Chrome versions 53 and earlier.
Starting February 8, 2017, we will show a banner at the top of the Gmail interface for users who are still on Google Chrome Browser v53 and below to encourage upgrading to the latest version of Chrome, currently on version 55.
The blog post says that the reason for this change is the number of security updates that Google Chrome version 55 contains. The blog post also explains that Gmail users that are still on Windows XP and Windows Vista are the most likely to be affected, because v49 was the last released version which supported those operating systems.
Gmail will continue to function on Chrome Browser v53 and below through the end of the year. Users who remain on Chrome v53 and below could be redirected to the basic HTML version of Gmail as early as Dec 2017.
Are you using Chrome on Windows XP? Find more details about this change here.