Anonymous FTP user cannot upload

I'm having trouble with anonymous user uploading files via FTP to my OS X Server system. The FTPServer is set up to allow anonymous access, and able to login and download files as anonymous without any trouble. Also, regular users, those with usernames and passwords on the system, can login using their own credentials and upload files.

The problem is that anonymous users can't upload files to the server - they receive a permission denied error:

553 /Upload Files Here/coreftplite1.3.exe: Permission denied.. (Upload)

Thanks in advance.