With Windows Server 2012 R2, Microsoft has built in a reverse-proxy feature. The Web Application Proxy securely publishes internal resources out to the Internet for access by both corporate-owned ...
I've got a customer who has 40 users on Office 365 E1, recently transitioned from BPOS. Right now they don't have an on-premises server at all; therefore, no AD - just workgroup with a QNAP NAS.