Emails are funny, they look so simple and we often take branded emails for granted, easily passing them by or sending them to the junk pile, but they are a lot more complicated than one would think. Unfortunately, with so many different email clients and so many different devices that we check our email with, consistency is essentially impossible. Some allow certain elements while others simply do not. What should be allowed in emails is a touchy subject with strong opinions on both sides. For now, designers and developers are left to deal with sorting out the mess.