If you ever think of beginning to send out emails (e.g. newsletters), you might want to read these tips, do’s and don’ts for email mass sending and HTML emails. 

Example of the Best Practices link:

SpamAssassin will give you bad marks for spam if you:

• include the word “Dear” near the top of your message.  (Crazy, huh?)
• send the mail from a long URL domain with 4 or more levels.

• http://commadot.com/the-holy-mail/
• http://commadot.com/email-best-practices/