Why Is My Email Filtered as Spam?

10 Simple Practices to Improve Inbox Delivery

No matter what email delivery service or SMTP relay you are using, some of your messages can end up in the spam folder. Internet service providers use different spam filtering techniques (which are sometimes pretty odd) to protect their users from spam.

So, you will absolutely have some emails filtered as spam or junk mail from time to time when sending your email campaigns.

There are tools like this free email spam checker that you can use to test your spam score, Inbox rate and Spam rate prior sending a real email campaign. The results may surprise you.

Well, while you can't tune up all of your emails to pass through every and each spam filter, you can follow these simple practices to improve your Inbox delivery:

1. Do not send from a free email address.

Instead of using your free personal email address from @aol.com, @hotmail.com or @gmail.com, use the email address from the domain of the company or organization on behalf of which you are sending the message.

If you are an individual marketer and do not have a website, you should register a domain, for example with GoDaddy, and use an email address from that domain for email marketing.

2. Use a consistent "From" email address.

Changing your "From" address too often is not a good practice. And the worst thing is rotating of email addresses in the "From" field which is a pure spammer tactic. Keeping your "From" details consistent helps build your good sender reputation.

We suggest changing the Mail From only if your current sending domain has a bad reputation which causes your emails to be filtered as spam. Restoring the sender reputation is not easy and is time-consuming. In this case, the solution could be registering a new domain and use that domain for your mailings.

3. Do not send only a graphic or image.

We've seen many users sending a beautiful HTML email containing one big image only. However, this is a sure-fire way to have deliverability issues because many spam filters look at the HTML part and plain text part and if the plain text part is missing or is too short compared to the HTML part, the email is considered spam. Thus, you should design an email with text and images. Do not use an image alone.

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4. Check links in your email.

Spam filters look at the URLs that you are sending. If a URL contains a domain that is blacklisted or has a poor reputation, you will be penalized. Plus, you should avoid using URLs that contain folders with 1-2 characters (such as http://www.domain.com/e/something/ or domain.com/es/) as some spam filters will see that as a negative thing.

Moreover, do not include links produced by link shortening services, for example, http://bit.ly/1NBfTpQ. Your links should be full paths to real pages.

5. Check your HTML.

Incorrect or broken HTML tags can reduce your Inbox delivery. Do not copy content directly from Microsoft Word, Excel, Powerpoint, etc. because these applications will add additional unwanted characters to your message source. And in addition to a broken HTML, your messages will be rendered correctly only in Microsoft email applications (Outlook etc.).

So, take the time to code your HTML correctly. If you are not an email designer, you can search for responsive HTML email templates on the Internet and buy some templates that meet your theme.

6. Do not include Javascript, submission forms, or video clips into your email.

This is a direct way to get filtered. Instead of sending such a stuff in the email, put it on your website and in the email send a link to the page where people can find it.

7. Do not use spam trigger words and phishing phrases.

You should remember that a spam filter does not like commercial advertisements and promotions. Though it doesn't mean that your email will end up in the spam folder only because you used a so-called trigger word, better if you avoid or use words that are common to promotion emails sparingly.

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Phishing emails are sent with the purpose to steal the recipient's identity by making them click on a fraudulent link. Commonly phishing emails look like legitimate emails sent from a service you trust, for example, your bank or a website you visit. Thus, you should avoid using phrases that are common to phishing attacks.

8. Do not send to inactive contacts.

It plays a big role in email delivery how your recipients act upon your message. So, you'll want to segment your list, separate inactive users and exclude them from your campaign. Focus on your active contacts to increase your Inbox delivery.

You’ll want to measure inactivity based on the volume of emails sent, not on the time frame. Thus, instead of asking “Did they open an email within the last 6 months?” ask “Did they open any of the last 10 emails I sent them?”

Try to wake inactive users with incentivized reactivation emails to determine whether or not they are still interested.

If they do not respond, as part of good email list hygiene stop sending to those people but NEVER DELETE SUBSCRIBERS from your base. You can always use those emails for retargeting people via Facebook or Google Adwords.

9. Check your sending IP against blacklists.

IP blacklisting is often the real problem that prevents your emails from reaching target recipients. So, you should do a regular check of your sending IP against blacklists and go through the removal process if the test reports blacklisting issues.

Besides public blacklists, your IP can be blocked by a particular ISP. Gmail, Hotmail, Yahoo!! and other providers maintain blacklists of IPs seen to send spam to their users.

Below are good guides you’ll want to check to learn how to find out if your sending IP is blacklisted by Gmail, Hotmail, or Yahoo! and how to request the removal:

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How to Remove Your IP Address from Gmail’s Blacklist
How to Remove Your IP Address from the Hotmail/Outlook’s Blacklist
How to Remove Your IP Address from the Yahoo!’s Blacklist

10. Maintain a healthy list of contacts.

Your bounce and spam complaint rate do matter. They affect your sender reputation which, in turn, affects your Inbox delivery. Thus, you should have a working process of handling bounce and unsubscribe requests after each mailing to ensure that you send emails to the users who actually want them and like them.


If your Inbox placement and spam filtering test reported many placements to the "spam" folder, the first step you should start your investigation from is changing elements in your email and test the email delivery after each change.

For example, re-write the Subject line and test. Still many "spams"? Remove graphics and test again. Didn't help? Delete links and test again. Still filtered or blocked? Re-write the content and test. By testing different subjects and email contents, you can find the best email copy that you can send to your subscribers.

If changing the message content does not help, so the problem is in your sending domain, IP address, and sender reputation. In this case, you have to change the Mail From. You can register a new domain close to your main domain (for example, emailyourdomain.com) and use that new domain for email marketing.

Check this post to learn more about email delivery, good and bad sending practices, and possible causes of deliverability issues.

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Julia Gulevich is an email marketing expert and customer support professional at GlockSoft LLC with more than 15 years of experience. Author of numerous blog posts, publications, and articles about email marketing and deliverability.