Default "Appy Mail" adverts when home button pressed. HELP!!!

So lately, my m8 has been getting these weird full screen pop up adverts and I can't seem to get rid of them for some reason. I have downloaded Zoner Mobile Security but even that has failed to find the problem, resetting the phone has also not worked. Anyone have an idea how I can stop this from happening? It usually occurs when pressing the home button or back button around once every hour or two.
Sent from my HTC One_M8 using XDA Free mobile app
Attached Thumbnails
Click image for larger version

Name:	1403987860516.jpg
Views:	19
Size:	33.6 KB
ID:	2822771