How to write emails that avoid SPAM filters

What is an email spam filter?

An email spam filter generally uses technologies like artificial intelligence and machine learning to detect unsolicited, unwanted, virus-infected messages (usually known as spam) and prevent them from reaching the recipients email inbox.

While it affects where the email goes inside the recipient’s email system, it does not impact your email delivery rate, which is based on how many emails are delivered. Since the spam-identified emails are delivered, the diminished access to them usually affects your overall email open rate.

The spam filter evaluates one or more factors about an email message to determine if the email should go to the primary inbox or the junk folder, including:

  • Subject lines that appear false or suspicious
  • Senders with blacklisted IP addresses
  • Spam-related words or phrases in the body of the email
  • Input from email recipients who mark certain emails as spam

You can’t totally escape spam filters, but you can follow these 10 steps to lower your spam scores and enhance email deliverability.

1. Maintain your IP reputation

Your IP address reputation is a huge factor in email deliverability. If you send an email campaign from a newly created IP address to a high volume of recipients, email service providers like Gmail, Apple Mail, Microsoft, and Yahoo, etc. may hesitate to allow your email to be sent to the recipient’s inbox.

You should warm up the IP address by sending a low volume of emails at first for a short period of time, ie a month or two and increase the quantity of emails you send over time.

Building your IP reputation slowly helps email service providers better understand your sending behaviors, email list accuracy and cleanliness, and how subscribers respond to the emails you send. If your emails have a positive delivery result (users don’t mark them as SPAM, users open/read them), email service providers are more likely to deliver them going forward.

2. Avoid trigger words or misleading subject lines

The words used in your email can trigger spam filters no matter what your original intention was. Phrases like “earn extra cash” or “increase sales” often get caught by email filters. Pay careful attention to every word and phrase you use, from the subject line to the body copy.

A 2016 study from Litmus found 54% of those surveyed reported being deceived by misleading subject lines to open a promotional email. When deceived, recipients also are more likely to flag your emails for the spam folder. Your best bet is to craft strong headlines and sidestep spam words.

If you’re not sure what words work best and which one’s don’t there is lots of great content on the internet to help you.

3. Ask your subscribers to add you

When they sign up, ask your subscribers to add your email address in their approved contact list (i.e., primary tab).

If they do add you to their contacts, it helps them and other subscribers see your emails. Including you on their OK-to-receive list, a trust signal automatically gets sent to service providers like Gmail or Apple Mail, which reduces your email spam score.

4. Don’t use all uppercase letters or over use punctuation in your subject lines

Write your subject lines in all lowercase letters, except for maybe the first letter. Also don’t over use punctuation ie CHECK OUT THIS GREAT OFFER!!!!

Write subjects that are direct and to the point and gives the recipient an idea of what the email is about. Don’t use more than 30 characters in your subject line.

5. Send value-packed content

You’ve taken steps so your content is more likely to appear in the inbox, but the job isn’t done. Now you need to wow your subscribers every time they open your email.

Email service providers like Gmail look closely at the engagement your emails receive from your subscribers. If your emails have low open and read rates, subsequent outreach might get sent to the promotions tab or even end up in their junk folders.

Personalization can be helpful in creating a wow perception. Create clean and professional looking emails, but don’t go overboard on graphics/image use and don’t insert too many hyperlinks.

Keep your email design consistent so your recipients will recognize it every time they receive it. Most importantly ensure you are sending content/information that your email recipients wants to read, not necessarily content you want them to read. The more valuable they find your content, the more likely they will be to read it and engage with it.

6. Forego attachments

If you’re inclined to attach a document with more information, a special coupon, pdf brochure, etc., DON’T DO IT. Attachments not only mean it takes longer to download the email, they often lead the email directly to a bounce or the spam folder. You’re better off uploading that document to your website and creating a hyperlink to that file, for the recipient to click on to view/read, etc.

7. Follow the law

Most countries have anti-spam laws (CAN-SPAM ACT, GDPR, CASL, etc.) to protect their residents’ data from spammers.

If you have U.S. subscribers, compliance with the CAN-SPAM ACT should be your top priority. Among the requirements:

  • Don’t use any false or misleading sender names. The sender should come from an actual person on your team and registered to a valid domain name.
  • Provide your postal address. It can be your current street address, post office box registered with the U.S. Postal Service, or a private mailbox.
  • Honor opt-out requests promptly. When subscribers tell you that they don’t want to receive more emails from you, remove them.

Look to each country to determine its specific anti-spam guidelines and laws.

8. Use proper text and image ratio

Spam filters block image-heavy content. Even if they don’t, some recipients use email providers that disable images by default.

Avoid using only image-based content. Mailchimp advises a ratio of 80% text to 20% images in an email. Limit your use of images to no more than three.

9. Avoid inactive subscribers

Some subscribers will be inactive no matter how often you reach out to their inbox. It may happen because they changed their email address as 31% do in a year. Or they may have lost interest in your content because their needs have changed or they don’t have time to consume them.

At this stage, you have some pretty good ideas on what you should do and shouldn’t do.

Treat subscribers who haven’t opened your emails in at least six months as an inactive subscriber. Your list will be cleaner and your emails are less likely to get flagged by spam filters.

We suggest adjusting your send frequency based on their activity before you delete their email addresses:

  • After 30 days, send mid-frequency emails.
  • After 60 days, send low-frequency emails.
  • After 120 days, send a re-engagement campaign.
  • If they still do not engage, remove (or sunset) them.

Remember email service providers can determine if your recipients are reading/engaging with your emails, and if you continue to send to inactive or disengaged subscribers, it could hurt your sender reputation and get your emails marked as SPAM.

10. Use email checkers for spam scores

But if you still have some issues with these spam filters, spam testing should be the last sure thing you can do to beat the spambots.

Here are a couple of tools that will help you improve your email spam score based on the mistakes you’re making:

  • Omnisend offers a subject line testers tool that evaluates multiple criteria, including spam potential.
  • Mail-Tester rates your email on a spam score of zero to 10. It also details what’s good and what’s not about your email, so you know what to fix.