We've finally published our own URL Defense decoder.
If you're using URL Defense in your Proofpoint Essentials instance and want to decode your link, just visit our decoder page to find out where the link really points to. The decoder also tells you if the site is blocked by proofpoint or not so you don't need to actually _click_ on the link and risk getting a drive by download installed on your box.
https://www.vircom.com/urldefensedecoder/