How to Avoid Content Filters

This article applies to:

You’ve crafted the perfect email for your next email marketing automation. Complete with an attention grabbing subject line, compelling copy, and irresistable call-to-action. You’re positive click rates will be through the roof! Unfortunately however, you find out your email has been filtered as spam and sent to the junk folder, or it’s been dropped by the receiving provider. Why did that happen?

What is a content filter?

When an email is sent, it goes through tons of spam filters on the provider level. This means providers like Gmail will scan and hide emails from their users that they believe to be objectionable or harmful by not accepting the email into their servers, or accepting it and placing it in the junk folder (not to be confused with tabs like promotions or social - tabs are considered part of the inbox). Overtime, they’ll learn their users’ behaviors and continue to improve their filtering logic. For example, if Gmail notices a user never engages with ABC Co. emails, or worse -- it’s frequently marked as spam, they’ll proactively send future ABC Co. emails to the junk folder so the user never has to see it. In a world where a majority of commercial emails are spam, email providers are cracking down to protect their users.

Although providers keep their filtering algorithms pretty secretive, we’ve got a pretty good idea of what factors are included. Keep these factors in mind as you review and improve your marketing practices. 

When you’re ready, run your email through mail-tester which grades your your email and provides helpful suggestions before launching your automation.

High Risk Industry

Some industries’ email content result in higher-than-average spam complaints, which negatively affects deliverability for the rest of our customers. In order to mitigate this risk, we do not allow these industries.

Sender Domain Health

Your domain health plays a large role in your overall email reputation which factors into your inbox placement. Your email reputation, similar to your credit score, is created by your habitual email marketing practices just like how your credit score is determined by your financial practices. Prior to purchasing a house or car, you would check your credit score to ensure you’re in good standing. The same is true for launching an email automation; check your domain health first.


  2. Click on ‘blacklists’

  3. Enter your business domain

  4. If you find yourself on a blacklist, follow the delisting instructions on the blacklist site prior to sending your email.  

Link Health

Did you know the links included in the body of your email are checked as well? While you’re checking your domain health in MxToolbox (above), check all the links in the email as well.

Keywords in Subject Lines and Body

It makes sense with the history of spam that the email industry has been able to curate a list of possible ‘spam’ words. Even if you use one of these words in a legitimate email that your recipients expect and want, it can still contribute to the possibility that your email will be marked as spam.

Examples of Spammy Words:



Certain keywords can trigger spam filters such as:


Free money/ offer/ quote

Great offer

Stock pic

Instant Access

Check out this list of The Most Common Spam Words. 

Unsubscribe Link

Make it easy for people to unsubscribe! Don’t attempt to hide the unsubscribe link by adding extra spacing. If your recipients cannot find the opt-out link they will resort to reporting the email as spam -- which is even worse. History of increased complaint rates can also decrease your email reputation.


Some filters can be triggered based on the formatting or images within the email. A couple recommendations:

  • Maintain a text to image ratio of 80:20.

  • Be consistent with branding, content, and formatting so customers are familiar with your emails and will expect it.

  • Refrain from using short URLs, which is often associated with spam.

Following these tips does not guarantee your emails will always land in the inbox and never be flagged by a content filter. Ultimately, the best way to stay away from spam filters is to testtest, test!