This is a fantastic intro to the variety of different key points you need to be taking into consideration when sending email. Great post Varius and, I'm sure, a welcome addition to the GFY Education series.
The only thing I would add is a bit of verbiage on content filtering and email clients... The big ones (Yahoo, Gmail, Live Mail, etc...) will weight your email based on content that is seemingly ok... e.g. Special Offer, Limited Time, Act Now, etc...
Great writeup, very solid
