Very close to success, my app now sends base64-encoded fax and it IS received on the other end.
The problem is that the fax received appears in RAW FORMAT--similar to what you might see if you opened a .pdf with notepad.
I'm going to attach the relevant portion of my C# code. Perhaps there is something wrong with the way I'm populating the DocDataType, DocumentType, ContentPartType, &/or ContentsType?
I'll also attach the PDF which is received. It IS a PDF, but it actually contains the raw PDF contents.
Cheers!