Problems with url rewrite of links

Hello,

I am having problems with url rewrites in mails. When I create link in mail (for example http://www.domain.com/category/article.html) it is then automatically translated to http://www.domain.com/sendy/w/9. But when customers receive this email and click on link in is not translated back to http://www.domain.com/category/article.html. It stays http://www.domain.com/sendy/w/9

Could you help me with this situation?

Thanks