The bottom line is that if you send email campaigns, you will most always run into spam filter issues. On average, you can expect 10-20% of your emails to get blocked, mostly due to overzealous spam filters and user settings. The unfortunate fact is that innocent email marketers who send permission-based emails get spam filtered all the time.

Unfortunately, there is no quick fix. The only way to avoid spam filters is to understand how they work...

Spam filters look at a long list of criteria. In particular, they scan for spammy phrases like "CLICK HERE!" or "FREE! BUY NOW!". They assign points each time they see one of those phrases. Certain criteria get more points than others.

Here are some sample criteria from Spam Assassin:

  1. Talks about lots of money (.193 points)
  2. Talks about opting out (lowercase version)
  3. Gives a lame excuse about why spam was sent
  4. Claims you can be removed from the list
  5. Contains urgent matter (.288 points)
  6. Money back guarantee (2.051 points)
  7. Why Pay More? (1.249 points)

Click here for a complete list of specific criteria from Spam Assassin.

If your campaign's total "spam score" exceeds a certain threshold, your email is flagged as spam. The threshold is different for every server. It's determined by the person who installed the spam filter software. If the person is really sick of spam, they'll set the threshold extremely low and about everything will get filtered.

The list of "spammy" criteria is constantly growing and adapting, because spam filters "learn" what junk looks like, every time someone clicks the "This is spam" button in their email program. Spam filters even sync-up with each other online, to share what they've learned.

We recommend that you avoid these common mistakes:

  1. Using phrases, like "Click here!," "Once in a lifetime opportunity!" or "Free"
  2. Multiple exclamation points!!!!!!
  3. USING ALL CAPS (especially in the subject)
  4. Coloring with bright fonts like red, or green
  5. Creating an HTML email that's nothing but one big image, with little or no text (since spam filters can't read images, they assume you're a spammer that's trying to trick