Drupal Multilingual Emails
If you installed the Internationalization Module, you should have a sub-module called "Variable translation". If enabled, go to admin/config/regional/i18n/variable and choose the variables which you would like to translate. 

In your case this would be the ones in the "User Emails" tab. Once checked and activated go to the user e-mail page (admin/config/people/accounts) and click on the different language links at the top of the page to translate.