[xwiki-users] Error about "SendPageByEmail Application"

Hi ,all. I have added SendPageByEmail Application, but when I sent a mail it told me "The page has not been sent. There might be an error in the email addresses you entered". In the page ,(http://code.xwiki.org/xwiki/bin/view/Applications/SendPageByEmailApplicati on) it said that In order to work properly, it requires the following conditions to be met : * The MailSender <http://code.xwiki.org/xwiki/bin/view/Plugins/MailSenderPlugin> plugin must be up & running on your wiki instance * You must have a SMTP server properly configured * The panel has to be saved by a user with programming rights. I have set up an Outgoing SMTP Server, and I think SMTP server work well. So the problem maybe MailSender plugin. How to install the MailSender plugin? I think I don't need to install it, since I use XWiki Enterprise 1.5 which has contained this plugin. http://code.xwiki.org/xwiki/bin/view/Plugins/MailSenderPlugin)