Microsoft gave notice this week that Exchange Server 2007 will be falling out of support in less than a year.
Exchange Server 2007 will pass Microsoft's "extended support" milestone on April 11, 2017, per Microsoft's lifecycle support page. And that date also applies to its Service Pack 3 iteration. The loss of extended support means that the server won't receive updates and security patches from Microsoft. The servers continue to work, but potential vulnerabilities won't get patched. Microsoft sells "custom support" as the only exception to this policy, but it's a costly temporary option.