Windows 7 Professional/Ultimate/Enterprise SP1 (32-bit & 64-bit)
Windows 2003 Web/Standard/Enterprise/DataCentre Editions (32-bit & 64-bit) (Abyss Only)
Windows 2003 R2 Web/Standard/Enterprise/DataCentre Editions (32-bit & 64-bit) (Abyss Only)
Windows 2003 SBS (Abyss Only)
Windows 2003 SBS R2 (Abyss Only)
Windows 2008 Foundation/Web/Standard/Enterprise/Datacentre (32-bit & 64-bit)
Windows 2008 R2 Foundation/Web/Standard/Enterprise/ Datacentre (64-bit)
Windows 2008 SBS (64-bit)
Windows 2008 SBS R2 (64-bit)
Windows 2011 SBS Essentials/Standard Edition (64 bit)
Server 2012 Essentials works perfectly. Had it working since prerelease and now in the released version. No problem whatsoever but there is a trick to get the SMTP relay working so 3CX can send alert emails. Again, works perfectly.