You might want to Stop your Send Port but leave it Enlisted. Then, check out the message contact properties using HAT. You are looking for File.ReceivedFileName. That’s what controls the %SourceFileName% macro. I thought it was there for FTP – but maybe not.
All you would need is a very simple pipeline component to promote your FTP files name into File.ReceviedFileName. I think FTP has it’s own file name called http://FTP.ReceivedFileName or something. That’s what you would need to set to File.ReceivedFileName.
Make sense?