Earlier today, a subscriber to my free newsletter asked me to critique his marketing email. (I do this as a free service to subscribers.) During our conversation, I felt the need for a complete list of the rules for effective email marketing. Here they are:

1. Prune your list mercilessly.

It’s not the number of email addresses in your list that count; it’s the percentage of email addresses belonging to prospects who might buy from you. Delete addresses that don’t open your emails and make it easy for uninterested “prospects” to unsubscribe.

2. Send emails during off hours.

Numerous studies have shown that marketing emails are much more likely to be answered if they are sent when prospects are not juggling all the daily emails that get traded during normal work hours.

3. Have a short, relevant Subject line.

Numerous studies have also shown that emails are more likely to be opened if the Subject line is 2 or 3 words, as opposed a sentence. Ideally, the teaser (the first 20 words of the email; see #5 below) should complement and reinforce the Subject line’s relevance.

4. Use the recipient’s first name.

Unless you’re marketing to a culture that values formality, start your marketing email with the first name of the prospect, followed by a comma. No honorific (like “Mr.”) and absolutely no “Dear…” Write as if to a colleague, not your Great Aunt Mable.

5. Pack a benefit into first 20 words.

In most email readers, the Inbox display includes the sender, the time sent, the Subject line, and the first 20 words (or so) of the email. Prospects decide whether to open your email based on those four elements.

6. Don’t pretend intimacy.

Stock phases like “Hope you are having a great summer” are not only insincere (why would you, a stranger, care?), they uselessly consume the valuable visual “real estate” that appears in the inbox summary of the email.

7. Show your uniqueness.

Your email must create the impression that you, personally, are worth the prospect’s personal attention. Find something about you, your product or your company that might be uniquely interesting or compelling to the prospect. (But see #12 below.)

8. Write from the customer’s viewpoint.

Prospects are interested in themselves, their own careers, their own business, and their own customers (in that order.) They will shrug off and ignore any message that’s primarily about you, your business, your product, your enthusiasm, or your opinion.

9. Remove all features and functions.

In most cases, prospects have no idea why they would want or need any individual feature of your product or service. Unless (as is seldom the case) the prospect has already studied your product category, a list of features is just visual noise.

10. Avoid unfamiliar acronyms and buzzwords.

Most prospects stop reading an email the second they see an acronym or technical term they don’t immediately recognize. For example, the term “CRM” means something to most business-folken; a term like “sales enablement system,” in contrast, means squat.

11. Be precise rather than abstract.

Statements like “saves money and time” or “improves productivity” are so colorless and vague that they fade into the background. Instead, provide a real example that shows exactly what the prospect is likely to experience.

12. Don’t toot your own horn.

People who don’t know you don’t believe your when you claim to be the best at anything. Worse, they’re likely to assume you’re either conceited or telling the opposite of the truth. For example, most people know it’s a red flag when a salesperson claims to be “honest.”

13. Try to start a conversation.

Unless you’re marketing consumer goods, the purpose of email marketing is to get into a conversation with the prospect, not to sell to the prospect. Start with trading emails, then segue in the second or third email into an appointment for a brief telephone call.

14. Ask a yes/no question.

The lowest barrier to getting into a conversation is a simple question that requires a yes or no answer. Important: answering “yes” must not be an attempt to commit the prospect’s time and energy. Example: “Is this of interest to you?” (good) “Can I send you some information?” (bad)

15. Include only 1 call-to-action.

The more calls-to-action that you stick into the email, the less likely it is that the prospect will take any of those actions. In almost every case, the most effective call-to-action will be for the prospect to reply to your email.

16. Never assign homework.

Contrary to popular belief, sending a prospect information will not convince them to consider your offering. Quite the contrary, sending a prospect “information” creates a barrier to having a conversation. You’re saying: “Read this and then get back to me.” Like that will happen.

17. Test, test, test.

First, test for open rate using different combinations of the Subject line and the first 15 words. Second, test for response rate using variations of yes/no questions. Finally, test for conversion rate by tracking which responses turn into purchases.