I am trying to use the C++ GetAttach function, using the following documented syntax:

  GetAttach(MCoreHandle, FolderNum, MessageNum, i, attach)

1st 4 parameters are declared as DWORD
5th parameter (attach) is declared as LPSTR

However, when I try to build I get the following error:

  error LNK2019: unresolved external symbol __imp__GetAttach@20

I believe @20 means that there are five 4 byte parameters, which seems right.

However, when I look at the MCore.def file included in your C++ sample, I see the GetAttach symbol listed as

  GetAttach@16

Similarly, if I open up the binary mcore.lib file in Visual Studio (2008) I see the symbols

  __imp__EMLToMSG@8.__imp__GetAttach@16.__imp__GetAttachCount@12

Has the function signature has changed?