Jan 31, 2006

Little Things Add Up for Spam Filters

Ever wonder what triggers the spam filters? One of the most popular server-installed spam filters out there is called, "Spam Assassin" and last year, we posted a link to a long list of things that Spam Assassin scans for.

We thought we’d revisit some of the most common things that will get innocent email marketers accidentally filtered…

Spam filters like Spam Assassin "read" your email. Kind of like how search engines read the content of your websites. Spam Assassin looks for spammy "clues" in your email, and then assigns a "score" for each clue it finds. For example, if you say something like, "CLICK HERE NOW!!!!" you might get 2 spam points. If you make it a bright red "CLICK HERE NOW!!!!" you might get 2.3 points. Then, if you say something really stupid like, "MONEY BACK GUARANTEE! ACT NOW! GET RICH FAST!!!!" you might get 6 points for that. Once your "spaminess score" hits the threshold (which is set by the server admin), your email gets blocked. Some people set the threshold high, some low.

Good email marketers would never commit 95% of the things Spam Assassin looks for. We’re talking about evil stuff, like forging email headers, faking links, etc. But there are a few things that seem to get accidentally included in lots of innocent email marketers’ campaigns. Here are the ones we see the most…

  • The phrase, "click here" is getting really bad. It was causing
    problems before, but it seems to be causing more nowadays. Especially
    be careful of using "click here" in your unsubscribe link. Don’t say, "Click here to unsubscribe." Switch it up with something more like, "You may unsubscribe from our list at any time" or simply,  "Unsubscribe from our list"
  • Using the word "test" in your subject line will often get you spam filtered. If you’re sending tests for clients, make your subject line look as real as possible.
  • As I recently posted, using "lorem ipsum" dummy text a lot in your message body will get you spam filtered, too.
  • Dollar signs are a big no-no. We realize this one’s really hard to avoid for a lot of businesses. So if you’ve got an email campaign with tons of dollar signs in it, make sure you’ve got other text in the email to "balance the equation." If you’ve got  a dollar sign in your email with a number that’s in the millions, you’re on thin ice. Be really careful not to do anything else risky, like using red fonts, too many exclamation points, etc.
  • Not enough text. If you only send an HTML email, you look like a spammer. Be sure to always include a plain-text version of your message (systems like MailChimp help you do this). Also, don’t send an HTML email that’s nothing but a bunch of graphics. The spam filters can’t read them to determine their content—so what do you think they’ll assume it is?
  • Don’t go nuts with font formatting. You get spam-points for making fonts huge. Also for making them tiny. And for coloring them red, blue, or green. Or using non-web-safe fonts. This seems to be a problem mostly with marketers who are using Microsoft Word to design their HTML emails. Don’t do that. Get a professional to develop a couple email templates for you.

Here’s an Excel spreadsheet of that Spam Assassin criteria list. We sorted it by "score" so that you can see what kinds of stuff it thinks are really bad. We also highlighted certain things in orange, which we think are easy mistakes to make…

Download spam_assassin_excel.xls


Don’t worry too much

Having one or two little dollar signs won’t get you thrown into the junk folder outright. Don’t fret if you break a rule or two. But if you also do other little things that look spammy—like using giant fonts, or coding sloppy HTML, or forgetting to include your plain-text message—all those little things add up.  Also, if you try too hard to avoid these rules, Spam Assassin seems to know, and think you’re actually a spammer. It’s like it can smell the fear on you. Just be yourself. Don’t be a jerk. Don’t spam. And just try to avoid the painfully obvious things that look spammy.

Finally, Spam Assassin posted their own tips for email marketers here.