[xwiki-users] newsletter extension doesn't send mail?

Hello I use newsletter extension (http://extensions.xwiki.org/xwiki/bin/view/Extension/Newsletter+Application) but I think scheduler doesn't work or mail doesn't sent... (My user subscribe at my newsletter) How can I log this to find the problem source? My xwiki user can sent mail from "share by email" menu. My catalina.out  display nothing. thxs