In order to make setting up a Gmail account on a mobile device as easy as possible, Google have long-since provided Exchange ActiveSync support. ActiveSync allowed iPhones, iPads, Andoid devices, Windows Mobile and any other ActiveSync compatible app to quickly set up a Gmail account and keep messages, calendars and contacts in sync across all their devices.
From today though, Exchange ActiveSync will no longer be available for Gmail. Google announced the news as part of a 'winter cleaning' programme and is recommending users switch to IMAP, CalDAV and CardDAV (for email, calendars and contacts respectively). Swapping to these protocols is not without problems for end users. For example some platforms (like iOS) don't support IMAP push email, and other platforms may not support CalDav or CardDAV at all.
Existing Gmail users won't have to change settings on existing hardware but everyone (new and existing Gmail users) won't be able to use Exchange ActiveSync on any new equipment they buy. Customers who need Exchange ActiveSync have the option of moving over to Google Apps for Business or moving to a hosted Microsoft Exchange platform that supports full ActiveSync to mobile devices.