If the text contains fragile commands, use the fancybox package and typeset the box first, using Sbox, then you can put the result into one of the fancier boxes:
\documentclass{article} \usepackage{url,fancybox} \begin{document} \begin{Sbox} \begin{minipage}{10cm} You received this message because you are subscribed to the Google Groups ``\LaTeX\ Users Group'' group. To post to this group, send email to \url{latexus...@googlegroups.com}. To unsubscribe from this group, send email to \url{latexusersgro...@googlegroups.com}. For more options, visit this group at \url{http://groups.google.com/group/latexusersgroup?hl=en}. \end{minipage} \end{Sbox} \fboxsep5mm \shadowbox{\TheSbox} \end{document}