How have you configured the Scope for this subscription? You probably need to use 'raised by an instance with a specific name' if you want to capture just one VM.
Although for future flexiblity, it might be best to create a group, and configure the scope for that. Even if the group only holds one VM now, in future you could add VMs for email alerting just by adding them explicitly to the group. No need to create new subscription every time. It depends on your requirements whether that's suitable.
In any case, I'd advise checking your scope criteria - make sure you have only the criteria you want selected, in this case 'instance with specific name' is probably best.
There is a good blog post from Kevin Holman here http://blogs.technet.com/b/kevinholman/archive/2012/04/28/opsmgr-2012-configure-notifications.aspx
on Subscriptions. Kevin's posts are always a wealth of great tips and tricks, well worth a read!
Hope that helps,