Assuming that you are following all the rules regarding permission marketing and opt-in (see page 99 in the book), here are some further tips on sending those follow up e-newsletters:
Consider upgrading from text-based to graphics-based (HTML). However, be careful not to get too fancy or it will lose the immediacy of e-mail. Also, do not increase the download time (see page 138).
Carefully identify who you are in the "from" line and also use a benefit-oriented "subject" line (such as "Bill Gates to Speak at Widget Expo").
Target the e-mail to the recipient by putting their name in the salutation. Also, personalize the body of the text, such as mentioning the recipient's firm.
Keep it short – no more than 200 words. Link to pages on your web site to give them more information.
Don’t look like a spammer – keep your tone friendly and informative. Avoid overblown language.