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Creating Spam-Filter-Friendly E-mails


Have you ever sent a beautifully written, compelling e-mail to your constituents, only to have several of them tell you that they never received it? The messages didn't bounce back to your in-box, so what happened?

Your message may be stuck in a spam filter. Spam filters are becoming more powerful to combat all those unsolicited mortgage ads, stock tips, and—ahem!—other annoying e-mails that clutter people's in-boxes. At the same time, however, they can prevent legitimate messages from reaching their destinations. By understanding how spam filters work, you can increase the chances that your e-mail won't end up in cyberlimbo.

Spam filters commonly work under a score system that assigns positive (spam) and negative (not spam) scores to a list of trigger words or phrases. When your e-mail contains a certain number of points, it's classified as spam. Some words and phrases count for more points than others, and the number of points a message can have before it's considered spam varies from server to server.

What Spam Filters Look For

Here are some of the most common items that receive points from spam filters:

  • Images accompanied by little or no text
  • Very long list of recipients
  • Large or very long messages exceeding a recipient's limit
  • Attachments
  • Colored backgrounds
  • Large fonts
  • Colored fonts
  • Messages created with Microsoft FrontPage
  • Punctuation in the subject line
  • Words in ALL CAPS in the subject line
  • Trigger words or phrases in the body or subject line, such as "click," "free," "guarantee," "limited-time offer," "urgent matter"

Where to Go for More Information

If you send your bulk e-mails through an external service, contact your provider for the latest information on creating spam-filter-friendly messages. Your Internet service provider may also have good advice.

You may find the following articles helpful. More resources will certainly be created in the future, especially as spam filters identify new trigger words and phrases. In the meantime, we found these articles especially useful:

Julian Ma, January 2007
© 2007, Philanthropic Research, Inc. (GuideStar)

Julian Ma is an undergraduate at the College of William and Mary. He was a communications/marketing intern at GuideStar during the fall 2006 semester.
Topics: Communications