Write file to remote computer

 I have a web application which will be running on the intranet. It basically takes some input and writes data to table and also creates a file. The problem is I want to create this file on a computer sitting on DMZ (outside the intranet). The target computer is not joined to a domain. Currently if I try to write the file, I get access denied error message. How do I get some sort of authentication?
Impersonation is not going to work because I'm writing file outside the domain, so security token cannot be obtained.
 
Any help greatly appreciated!
Sandy
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