w3 validation error of shortcode generated form

Hello Stefano

First of all, thank you for that wonderful work of yours!

I implemented the newsletter in a site of mine and had the following validation error ( besides obsolete attributes ) The <p> does not seem to find and end </p> although it is present? Maybe remove them after all ?

http://validator.w3.org/check?uri=http%3A%2F%2Fwww.solardecathlon.at%2Fnewsletter&charset=%28detect+automatically%29&doctype=Inline&group=0