How Spam Filters Work?

Spam filters consider a long list of criteria when judging the “spamminess” of an email. They’ll weigh each factor and add them up to determine a spam score, which then determines whether a campaign will pass through the filter. They might look for spammy phrases like “CLICK HERE!” or “FREE! BUY NOW!” Then they'll assign points every time they see one of those phrases. Certain criteria get more points than others. Here’s a sample of criteria from SpamAssassin:

  • Talks about lots of money (.193 points)
  • Describes some sort of breakthrough (.232 points)
  • Looks like mortgage pitch (.297 points)
  • Contains urgent matter (.288 points)
  • Money back guarantee (2.051 points)

If your campaign’s total “spam score” exceeds a certain threshold, then your email goes to the junk folder. Passing scores are determined by individual server administrators, so unfortunately, what passes some filters doesn't pass all of them. As for that list of spammy criteria, it’s constantly growing and adapting, based on—at least in part—what people identify as spam with the "Mark as spam” or “This is junk” button in their inbox. Spam filters even sync up with each other to share what they’ve learned.

Spam filters don’t publish their filtering practices, as doing so would give spammers the knowledge needed to bypass filters and harm their users. But even though there's no magic formula, we can still help you avoid common mistakes that result in emails landing in junk folders.

Was this answer helpful?

 Print this Article

Also Read

Spam - Overview

If you send enough email campaigns, you’ll inevitably run into spam filter issues. According to...

Content Filtering - How does it work?

Content filtering is often hard to explain to people, and I’m not sure I’ve yet come up with a...

A List of Common Spam Words

One of the fastest ways to end up in a subscriber's spam folder or junk folder is to load your...

When does Email Address go Stale (Stale List)?

Every mailing list can go stale when it isn't used regularly, even if the subscribers were...

What is Spam?

There are a variety of definitions and interpretations of the word itself, but at its core, spam...

Powered by WHMCompleteSolution