How to Stop Your Email Newsletter Being Blocked by Spam Filters

Email newsletters are a critical tool in the armoury of every online publisher. They should be used both in the sales process and to build loyalty. Therefore if you find that a lot of your emails are not being delivered you must take the time to understand why.
The number one reason why email newsletters don't get delivered is because they are blocked by spam filters.

Therefore it's important that you know why this is and how you can reduce the chance that it happens.

Spam filters are like bingo cards. The have a checklist and if an email ticks enough boxes on the scorecard … bang … the door is slammed in its face.  Unfortunately every spam filter is slightly different.

However if you follow these guidelines your newsletter should slip past the gatekeeper every time.

Tip #1    - Check All Email Copy Using a Spam Checker Tool

Spam checker tools put your email copy through a spam filter and create a report about how it was viewed. This will instantly tell you if you have problem. Most good commercial email services have a spam filter built in. If yours doesn't there are some free tools you can use:


Tip #2 – Know What Words Spam Filters Look For

Spam filters look for certain words, phrases, layouts and email characteristics.

The number one cause for blocking an email is the use of words that commonly appear in spam. Some are obvious like free, Viagra, and get rich. Some are not so obvious like opportunity, amazing and compare.

Tip #3 – Think Carefully About Your Subject Line

Every spam filter is weighted to take a long hard look at the subject line. Avoid using any of the spam filter words in this sensitive field. Also avoid capital letters and exclamation marks.

Tip #4 – Text-Based Emails are Best

Many email newsletters are html with lots of images. They look slick and professional as marketing material should. However be aware that html emails are more likely to get blocked. Good email services will create a version of your newsletter in both html and plain text to increase the chance of getting through.

Tip #5 – Avoid all image Emails

Some emailers put their whole message in a big image; big mistake. Not only the spam filters likely to take an immediate dislike to the email, but also a lot of firewalls are programmed to strip images out so recipients can end up with a blank page.

Tip #6 – Avoid Attachments

Many viruses are hidden in attachments so spam filters and firewalls are often programmed to block attachments from unknown email addresses. Avoid attachments if you can.

Tip #7 – Avoid Using BCC

Ifd you put dozens of names in your BCC (blind copy) field in your email programme the newsletter could be marked as spam.

Tip #8 – Don't Use Color Text and Background Colors

If you use color text or color backgrounds in your newsletter the spam filters will wag their fingers and look for other questionable characteristics and reasons to block you.

Tip #9 – Most Spam Has a Small File Size

Most spam has a file size of less than 20k. Therefore newsletters with quite a lot of text are more likely to get through. The ideal file size is 20k – 50k.

Tip #10 – No Viruses

Sounds an obvious point, but if you are sending an email from your own PC, make sure you have anti-virus software loaded. The quickest way to get blacklisted by every firewall is to distribute a virus.



I would recommend using a good email service like Constant Contact, Lyris or Exact Target to distribute your newsletter. It is too important to screw up. Getting blacklisted can take a huge amount of effort to recover from.

However even if you use a professional service you should follow these guidelines to increase the chance that your emails reach their intended destination.