What’s inside:

How spam filters work and how to avoid them. Topics include:

  • What is spam?
  • Spam filters
  • Email firewalls
  • Abuse reports

Legitimate email marketers who send permission-based emails to people who requested them get spam filtered all the time. Unfortunately, there’s no quick fix. The only way to avoid spam filters is to understand what spam is and how the filters work. This guide gives you the rundown.


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 assign a spam score, which helps determine whether a campaign will pass through the filter. If the score exceeds a certain threshold, your email will get flagged as spam and go straight to the junk folder.