2
Emailed news is currently not handled by a template (since it doesn't use the PHP internal mailer). Instead, you will find the assignment $mail_link in your news article template. It refers to line 115 of modules/news/article.php. This will allow you do directly modify the link generated with the "email this story" image.
If you are looking to modify the message sent, this is a langauge setting, found in modules/news/language/____/main.php (Lines 36-38 in english). You are looking for the constants _NW_INTARTICLE and _NW_INTARTFOUND.
Hope this helps, and good luck!
Always remember to make backups of your files you will be changing. You know, just in case.