Google says that starting with February 8, Chrome users will have to use version 54 or 55 (current) if they want to access their Gmail accounts.
Users on other Chrome versions, 53 and previous, will see a warning at the top of their browser, and Google doesn't guarantee that some Gmail features will work as advertised.
"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," Google explained in an announcement published yesterday.
This puts XP and Vista users in an unpleasant situation, as the only browser still supported on their operating systems now remains Firefox (ESR 45).
Mozilla, too, plans to stop providing support for XP and Vista users in September 2017, at which time there will be no more officially supported browsers that XP and Vista users can choose from.
This will not stop XP and Vista users from using deprecated browsers, but this will also expose them to numerous security threats.
Microsoft ended official support for Windows XP on April 8, 2014, and is scheduled to do the same for Windows Vista on April 10, 2012. Vista extended paid support will end on April 11, 2017.
Google says that Gmail users on XP and Vista could reliably use the stripped-down "HTML version" of Gmail to continue reading and sending their emails.
The company also says that by December 2017, most XP and Vista users could be redirected automatically to the HTML version, as Gmail expands with new features.