I think GetAddrInfoW requires Windows 2k "Pro". Is that what you have?

If not, then maybe this discussion thread might help: http://groups-beta.google.com/group/...4fa2051a673208

Or, it might relate to a known bug in atlsocket.inl. See this discussion thread: http://groups.google.com/group/micro...9ef573ae1d76e3

Incidentally, the exact opposite symptoms that you described (i.e., it doesn't work on XP) are described in this KB article, which also mentions your CSMTPConnection class: "BUG: Cannot Locate the Procedure Entry Point FreeAddrInfoW When You Run an Application on Windows XP" at http://support.microsoft.com/default...b;en-us;822334

Maybe it's related?

Mike