Hi Mike,
there are a few approaches here.
a) allow the upload to the NTWS, but then when a file arrives you can then move it off to your other server. At that point you could use anything - email, ftp, whatever. (you could even use a web client) - It all depends on what is on your main server.
b) you can send the file _directly_ to the main server, by just setting the URL of the save button on your form. However, this does imply a lot of "integration" between web pages on the two servers, as presumably the form contains more than just the uploaded file.
Of course, the question then becomes - what is the file for, and who needs to _retrieve_ it? (you can obviously create a link in the NTWS page to the file on the main server page if you like, if it's just simple file storage and retrieval.)
Cheers
Bruce