Changes

There are two related parts to email marketing: making sure that your content is in good form; and making sure that it is actually delivered which is purely technical in nature.

They are related in that all major email service providers (GMail, HotMail, Yahoo!, Comcast, Verizon, etc) scan email '''content''' on the receiving side with some heuristics to determine a 'spam' score in addition to other more 'technical' measures.