>I seem to remember that at some point, Microsoft removed the need for the Interop dlls. But it may have only applied to Office.

That might explain all this.

IAC, the usage of those two libraries is deprecated since two versions of Visual Studio which is sending warnings at every compilation. So, I guess it was time to move on with .NET component that would work in 64 bits. Now, I have the Web site running in 64 bits and that is a great boost of performance. It took about two hours to rebuild the class to support a new utility to read a MSG file.