http://litmus.com/blog/why-email-designs-break-rendering-guide-infographic/litmus-road-to-rendering-infographic
http://css-tricks.com/using-css-in-html-emails-the-real-story/
http://en.wikipedia.org/wiki/Email_service_provider
http://mailchimp.com/resources/guides/email-marketing-field-guide/
wayback
http://www.xavierfrenette.com/articles/css-support-in-webmail/
http://www.sitepoint.com/text-html-let-users-decide/
http://kb.mailchimp.com/article/why-bother-with-plain-text-emails
http://coding.smashingmagazine.com/2012/07/13/coding-qa-with-chris-coyier-code-smell-type-grid/