Yeah, those messages are associated with VZW's sync and connect feature that they take the liberty of signing you up for whenever you use anything but the native gmail app to set up email.
If you use the hTC client to set up one of the pre defined accounts on the selection menu this will happen.
Right when you fist set it up they ping you with a free message from Verizon reading something like Thank you for using the sync & connect feature...
You have to opt out of the feature to make these messages stop.
You can on the my Verizon website, but I don't remember exactly how to get straight to it.
Just when you look around for it hit stop/disable the sync & connect feature.
It is supposed show all your email accounts configured in one place so you can access all your mail.