If someone else might own the copyright to it, don't submit it. Outline is for reading pages that:
* you own the rights to,
* is in the public domain,
* constitutes fair use, or
* you have consent of the copyright holder.
It's unlikely to hold up in court; the servers of outline.com and their owners will likely be deemed as creating the unauthorized derived work.
You cannot sue a hyperlink that's floating around in the wild; you cannot prove who created that link.