File extention permissions

[Hyp8ri0n]

I hope you guys can help me. Since, this is the end all be all place to ask about plesk problems. I'm trying to setup a redirect for a game server. I've setup a domain pointing to the correct location of the file. The file can be viewed (listed) but Plesk only allows for .zip, .rar etc.. to be downloaded. The file I'm trying to download is a .pk3 extension file, which is a mod file for a game server. When the player joins the server and doesn't have the file it will point to the location of the file such as http://yoursite.com/mods/xxxx.pk3 <-- how can I allow download of the above extention?