Why some "shor links" do not be ok with rss programs?

Hi to all,

Just see and thanks to my boss to ask me how i work some of mimes redirections links are not ok in rss programs

i explain i make some redirections with some french pages
and when i want to submit my link in rss do not accept it ????????????

so why some "short link" are ok in rss programs and others no ????

do you have the same trouble please?

thanks