Email Design Tips to Avoid Spam Filters

Avoid spam filters to make your email campaign a success

Felix Higgs avatar
Written by Felix Higgs
Updated over a week ago

Well designed emails can help avoid spam filters and stop emails from being marked as spam by subscribers.

  1. Good Subject Lines

    1. Avoid using capital letters in the subject lines. Using all capital letters can be considered rude and disrespectful. Recipients may mark emails as spam and also alert spam filters.

    2. Use witty, inquisitive subject lines which will draw people's attention to your email.

    3. Use a question mark instead of an exclamation mark. Subject lines with a question mark have significantly higher open rates.

    4. Don't use trigger words that will hit the spam filters. Words such as 'free', 'best price', 'cash' and 'no obligation' are all associated with spam mail.

    Here are a few good subject lines:

    "Did you get what you were looking for?"

    "Hi [Name], [Question]?"

    "You are not alone."

2. The email body matters

Emails can be marked as spam based on certain content and images. With spam filters, the design, fonts, embed and images all matter.

a. Avoid using attachments. Attaching files such as Word and PDF documents will alert spam filters immediately. If you need to include these, provide a link or CTA to the documents locations.

b. Use regular fonts, minimal font sizes and minimal font colours. The majority of people prefer one font size, familiar fonts and colours.

c. Only include images that are relevant to the content and complement it. Too many images will increase load time and also affect deliverability rates.

d. Some recipients will allow the display of images while some block images. If the images are block, the email won't look so good. Make sure you add alt text which accurately describes the image.

e. Double check your spelling and grammar. This is essential for every good email marketing campaign. Poor spelling and grammar will affect your credibility and make it look unprofessional and hit the spam triggers. Take your time to ensure it is done right.

f. Simplify the unsubscribe. Don't forget to add a unsubscribe button or link to every email. It will help protect your ISP reputation and credibility with customers.

g. Image to text ratio. Ensure no more than 30-40% of your email is image content. Spam filers look for this and may mark your email as spam if the image content is too high.

h. Don't use URL masks. Making a URL shorter or masking the true URL is a tactic often used by spammers to hide the true destination of a link and may trigger spam filters.

Implementing these tips will help keep your emails out of the spam box and in your customers' inbox.

Other factors affecting email deliverability

  • Proper authentication - Ensure your email sending platform is properly authenticated with SPF, DKIM & DMARC

  • Bounce rate - If too many of your emails bounce (are sent to an inbox which doesn't exist or isn't available) this can affect your deliverability over time

  • Blacklists - monitor your sending addresses & ensure you're not added to any blacklists. If this happens take steps to ensure you're removed

  • List Health - Maintain a clean list of engaged subscribers, remove inactive & unengaged subscribers. Double opt in is also recommended.

  • Maintain a healthy IP reputation - Create a healthy IP reputation by gradually warming up your send volume and monitor & address any drop in sender reputation

Pro Tip - Testing your emails for spammy content before sending can help identify problems early, we recommend using Mail Tester for this.

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