Jim,

 

The next major version, SmarterMail 14.0, will be using .NET Framework 4.5 which is not ("easily") supported under Windows XP.  This version of SM will also end support of Windows Server 2003, since it too does not support .NET 4.5.

Windows XP is officially dead.  You can't even load patches released prior to the end-of-life date now.

 

Microsoft pulled all XP patch support in August, 2014, and all of the antivirus vendors have pulled all support for all of their antispam products.

 

Yes, I know there are tons of legacy applications which will not run on anything except Windows XP, but my recommendation to my consulting, and hosted, clients, is to upgrade to Windows 7, at the very least, as anyone connecting Windows XP to a live Internet connection at this point is asking for trouble.