Just leaked about a half hour ago, apparently. Links are pretty scarce at the moment. It's from the fbl_impressive lab, so I'm wondering if it's going to be the next public build.
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Ok I have an HP Spectre XT 15 touchsmart with IDT high definition audio drivers with beats. Recently when installing 10051 build. My sound and video would play fine then after a little bit my sound would start to slow down,crackle and lag. The video...
Read more: http://www.neowin.net/news/windows-10-build-10051-has-new-mail-and-calendar-apps
See also:
Windows 10 build 10051: A closer look at the new Mail app
Windows 10 10051: A closer look at the new calendar app