When a notification email is sent, it is generated by an event action. The out of the box action which sends this email has this text hard-coded in English. To send an email in a different language, follow these steps:
Go into Administration, Events-Rules-Actions.
Locate the appropriate action which sends the email.
Make a copy of this action.
Disable the out of the box action and make sure that the copy of the action is enabled.
Edit the copy of the action and change the text to the appropriate language.
Now, when the action is run, the email which is sent will be in the appropriate language.