Filters these days are much more sophisticated than the typical e-mail filters in Eudora and Outlook that can be made to delete an e-mail message that contains a "bad" word. Filters such as SpamAssassin look for patterns and add or delete points for certain factors. Then, if the total score reaches a predetermined level, the message is flagged as spam. By looking at what adds points (bad) and subtracts points (good), I've learned how to construct e-mails that will do better with the filters, if not escape them entirely.

Note: spam filters are a moving target, and my suggestions may not be as useful a few months from now. Moreover, the SpamAssassin defaults listed here can be (and sometimes are) adjusted by over-eager spam-adverse ISPs, so don't count on them. They're best used as a way of seeing what the filters consider bad or good, rather than as a precise measure.

I've found 20 different strategies that can help. Some of these are crucial; others are only of minor importance. But taken together they can help you get more of your legitimate opt-in e-mails through the obstacle course to your recipients.

1. Avoid E-Mail Software or Listservers Used by Spammers
Certain desktop e-mail listserver programs, as well as ASP hosted listservers, have developed a bad reputation for sending spam.

SpamAssassin looks for "fingerprints" of programs on its "bad list," and adds points to your spam score if it detects them. For example, any e-mail address that includes @email-publisher.com costs you 1.00 points. Employing various free web hosting services that are commonly used by spammers can hurt, too.

The desktop e-mailing software used most often by spammers (if it can be identified as such by SpamAssassin) is penalized from 3.0 to 2.0, in descending order: jpfree, VC_IPA, StormPost, JiXing, MMailer (Gammadyne, 2.73), EVAMAIL, IMktg, screwup1, Outlook 3.14159. GroupMail, hash 2. Group Mail (ver 2.0) is dinged 1.84. Other identifiable bulk mailers are penalized about 1.00 points. (Note: While I don't spam, I use Gammadyne Mailer routinely. The current version has no tell-tale headers identifying it as in some earlier versions. I am told Group Mail 3.x does not use such headers either.)

You might study e-mails sent out for any header lines that indicate the brand of mailer. You'll sometimes see this in the user agent and x-mailer header lines. If you find them, disable them or insist that the software vendor remove them. It is better to send e-mail from an unknown e-mail program than one which can be identified as used by spammers. Or use Apple Mail which has such a good record (spammers can't make it work well for them?) that your point score is reduced by 1.78. (Just kidding.)

2. Use Capitalization Carefully
Capital letters are seen as "yelling" and spammy. Excess capital letters cost you .21. I had been using capitalized titles until I found that I was being penalized for these. Since then, I've stopped using whole lines of capitalized type as headlines in my text newsletters. Instead I limit capitalization to partial lines only.

3. Keep HTML Simple

According to SpamAssassin, if your HTML message has more than 50% HTML tags (that is, has very specific formatting), you are fined 0.31 to 1.78 points. The lesson is to keep your HTML very simple. Highly stylized formats can hurt your score. Here are a few more elements to avoid, if possible:

An HTML table with a thick border (0.41 points)
JavaScript contained in the message (21 to .30 points)
HTML comments "which obfuscate text" cost 2.08 (whatever that means).
An HTML form in your e-mail message can also be costly. An "obfuscated action attribute" in an HTML form costs 1.00 point.

4. Watch Your Hyperlinks

SpamAssassin gives links a good looking over, so be careful.

Links without an http:// prefix cost 1.28. Oops. I've been shortening them, but does that spamify my newsletters? I hope not.
Don't link to URLs using IP address numbers instead of a domain name (3.1).
More on mailto links below under unsubscription systems.

5. Use Color Judiciously

Realize that high art is likely to cost you something. A font color tag that isn't formtted quite right can cost you .21. If you are using special font colors that aren't in the palette of 217 web safe colors, you are dinged .30 points. Hidden letters (same color as the background color) cost you .34 points. Beware the color police.

Black
0

Blue
.21

Red
.32

Gray
.33

Green
.41

Cyan
.41

Yellow
.42

Unknown color
.42

Magenta
.44


Black fonts are safe, but I'm not ready to desert color yet. I'll try to avoid using it in font tags, however. Rather I'll control color with style sheets and see if that helps. Unfortunately, many e-mail client programs don't handle style sheets very well yet. Also be aware that using a background color other than white is suspect, and racks up 0.317 points.