In email marketing, as in life, clarity trumps persuasion.
A more applicable definition as relates to email marketing is to be clear as to what is is you want the viewer to do, and back that simple message up with WHY they should do what you want them to do. We so often in life, and in email marketing, clutter and bury our real intentions with meaningless extra stuff, or vague calls to action.
Having internal clarity with what your objectives are, and then distilling that message down to something the end viewer can really use is the most important key to a successful campaign.
Other important factors of the email marketing medium are the aspects of personalization and conversation. Many times in email campaigns the advertisements look like mass-produced print advertising replicas. Take to heart the unique opportunity to use personal messaging and a more conversation-based approach, and I’m confident your campaign results will benefit.
Dr. Flint McLaughlin of MECLABS gave an interesting presentation on this topic Marketing Sherpa’s Email Summit 10′ which you can view here: http://www.marketingexperiments.com/images/multifiles/articulate/miami-summit-2010/player.html