Recently, on a copywriter’s board, one of the members posted this guideline regarding emails and autoresponders:

For clients who want a set number of autoresponders, I follow a certain structure most of the time:

• Begin with a story or interesting description.
• Include three links in the body.
• Precede each link with a question, if possible, or at least a short sentence.
• Include a P.S. that mentions one bonus or benefit that wasn’t mentioned in the body.
• The word length is usually 500 words.

For my own websites where the autoresponders are an ongoing thing, and not limited to a series, I don’t follow a set structure because my focus is on building a rapport, not on pitching something every single time.

Source: www.AnitaAshland.com

I thought that put things in a nutshell pretty well.