ADRMS IpcfEncryptFile can't process UNC path

Given that my excel file is in \\fileserver\everyone\, when I invoke IpcfEncryptFile, then I get an exception 0x8007007b.

If I map \\fileserver\everyone as let's say z:\, when I invoke IpcfEncryptFile, then it's successful.

I don't want to use mapped drives as this will only work when I'm logged in the server. My application is a windows service and it needs to work even when I'm logged off.

Has anyone had success using UNC paths for IpcEncryptFile function?

Update: After playing around a bit, having the excel (source file) in \\fileserver\everyone is ok. but, having the output directory in a unc path, let's say \\fileserver\everyone\encryptedByAdrms doesn't work.

If I set the output directory to let's say c:\temp\encryptedByAdrms, it will work.