> but they're... proprietary Everything you ever wanted to know about Exchange [1] (but were afraid to ask). I personally use SOGo [2] as a Exchange ActiveSync

> but they're... proprietary Everything you ever wanted to know about Exchange [1] (but were afraid to ask). I personally use SOGo [2] as a Exchange ActiveSync provider but I know OpenChange is a project to implement the entire Exchange stack. So I would not consider it proprietary. [1] https://msdn.microsoft.com/en-us/library/cc307725%28v=exchg.80%29.aspx?f=255&MSPPError=-2147217396 https://msdn.microsoft.com/en-us/library/cc307725%28v=exchg.... [2] http://www.sogo.nu/ http://www.sogo.nu/