XF 1.5 How to send user mentions by email?

I'm using user mentions often (I mean, when you write @username). I've seen that the user can see an alert, but seems that he doesn't receive an email notification.
Is there a way to sent him an email?

Thanks in advance.
OK, I have sucessfully installed it. Now I see it's an user option to choose whether if they receive or not in their alert preferences
For existing users is there a way to do a massive change in all users so they all receive them? (leaving the option to disable by themselves)