I use Seven and it works fine for me. Buckguin, it isnt a SMS notification app. It downloads your email and notifies you of any new mail. I use it for my Hotmail and Gmail.
They do have thier own forums and thiers mods are usually pretty quick to answer. You can find it
here.
I havent seen the same issue as you as I get notifications on new email but ONLY if it is in my Inbox. I have many folders in my Hotmail accounts and have setup 'rules' to seperate certain mail to certain folders. For instance I have all my notifications from this board going to a folder called 'PPCG'. Hotmail itself has options to notify you via SMS of ANY mail that comes in but since I have used Seven it no longer works. IDK if it is something on MS (hotmail) side or something Seven did.