29 August 2014
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How to avoid email spam filters

Let’s face it. You can’t avoid spam filters and you most probably won’t achieve 100% deliverability rate for your emails. Thanks to some hard working spam filters, it was found that an average of 10 – 20% (in some cases, even higher) of your emails or 1 in 6 emails do not end up in inboxes. Instead, they may turn up in the spam folders or even simply being trashed. Even if your emails were permission-based.

However, this does not mean that you can’t do anything about it. You can and here’s how.

What are spam filters?

First, let’s understand what spam emails are and how spam filters function.

According to Wikipedia, spam is defined as unsolicited or junk emails. Basically, it is an email that you receive from someone you did not know. Spamming involves the act of using electronic messaging systems like the Internet to send these unsolicited messages, usually in bulk, and usually to promote something.

It is not a spam if the email is from someone you know or a newsletter that you had signed up for. But sometimes the line gets blurred like when a friend’s computer is hacked by spammers and his email contacts (including yours) are being sent promotional emails. Or if someone uses your email to sign up for newsletter without your knowledge.

Spam filters, like the name suggests, are software which detect these unsolicited emails and prevent them from being delivered into the recipients’ inboxes. They are automated and are programed to filter out emails that meet certain criteria e.g. money matters, sales pitches and the use of images. If your email scores highly in this checklist, chances are it will end up in the spam folder or even go missing.

What you should avoid

Because of the increase of spam emails, mail servers’ spam filters have been configured to be on the lookout for spam or anything that looks like spam. Mail servers will accept and deliver spam-free emails but if they detected a spam email, they will refuse to deliver the email and issue a rejection notice or they may just simply ignore it. That’s how your email vanishes!

Here are some common mistakes that email marketers should avoid.

  1. Don’t buy or rent email lists

    Buying or renting emails are a form of unsolicited email.

    Firstly, you do not know where these emails came from or whether the owners are aware that their email addresses are being sold to online marketers. The emails could even be dead or inactive, which not only waste your money but will also damage your reputation!

    Secondly, even if the email owners agree to receive email communications in general, they did not agree or shown any indication that they want your emails. They might decide to delete your emails or unsubscribe or mark your email as a spam, which again, is not going to help your reputation!

    In short, do not buy email lists.

  2. Spammy email subject

    The email subject line is important because of 2 reasons:

    • Spam filters focus a lot on how the subject line is written to determine if the email is spam or not.
    • A well-worded subject line can persuade your recipients to open the email and hence, a higher email open rate.

    Our advice is to avoid spammy and suspicious words like “buy”, “money making”, “free”, “online marketing”, “click here”, “call now”, “apply now”, “order today”, “no obligation” and “This isn’t spam”. Instead, make the subject relevant to what you are promoting or a summary of your newsletter. This will also encourage your recipients to click and read your emails.

  3. Impersonal emails

    Filters look for impersonal emails which look as if you don’t know your recipients. So personalized your emails as much as possible. Try not to address your recipients by their email address. Instead, use the recipients’ first or last names. Not only will you make your emails more personal, you will also be able to “prove” to the spam filters that your emails are solicited.

  4. Spam triggering words in the content

    Getting the green light from spam filters for your subject line doesn’t mean that you can write anything in your message. Spam filters do search email contents for spam indications. Even if it doesn’t, you still want to deliver an informative message to your recipients. Therefore, do avoid spam trigger words here too.

    Further read:


    Using all caps is akin to shouting in email etiquette. You wouldn’t like someone shouting at you in real life so don’t do that to others in an email, especially if they are potential customers. Even though you very much like to get your recipients’ attention but shouting will only put them off. And not to mention, draw attention from spam filters.

  6. Large attachments

    While some attachments are safe like .jpg and .pdf files, try not to send them together with your email especially if they are large in file size. Of course, definitely not executable attachments like .exe files. Not only are they going to use up more resources, they may trigger spam filters or virus scanners. Instead, add call-to-action in your emails and link them to a landing page where the product details or downloads are located.

Email spam filters

What you should do

  1. Permission marketing

    Even if your customers gave you their email addresses, it doesn’t mean that they had agreed to sign-up for your newsletters. You should inform them about your marketing programs and seek their permission in writing like in a sign-up form or opt-in link via email. You can provide some promotions to persuade them to sign up, for example coupon codes or free downloads.

    You can even request to have your email address added into their contacts. This is called white list (as opposed to blacklist). Being white listed is like telling spam filters that you are a friend and not spam.

  2. Add text message

    Provide alt text message if you are drafting a HTML email or an email with images. Spam filters do not read images and thus, the lack of text may indicate that you are trying to “trick” the spam filter. Hence, your emails will have a higher chance of being blocked.

    Moreover, by default, majority email clients block images unless the owners choose to have the images displayed (which many of them don’t). Adding text will allow these readers to see a part of your email and hopefully, be tempted to read further.

  3. Maintain A Clean List

    Clean up and update your email lists constantly. Remove all those bounced, unsubscribed and invalid emails. Repeatedly sending emails to these addresses will only irritate these owners and they will mark you as spammer and this will eventually get your IP blacklisted.

  4. Send By Batches

    Sending a large quantity of emails at one shot will trigger spam filters to think that you are spamming or even a virus. What you should do is slow down and send your emails to your recipients in batches. Therefore, it is important to plan your marketing campaigns so that all your recipients will get the email by the time your promotion starts.

  5. Test Your Emails

    Last but not least, do test your emails by sending them to the email clients that most or all your recipients use. You should at least test read them on Gmail, Yahoo Mail, Hotmail and Outlook email client. This will ensure that the email will reach your recipients successfully and they can read them properly – your email will appear right and that no part was truncated or links missing.

As an Internet marketer, you have spent a lot of time drafting and designing emails and transforming them into impressively designed newsletters or announcements. But all these efforts will be lost if your emails do not reach their intended recipients. Spamming laws are getting stricter and even though you are a legitimate online marketer, you might still get caught.

Fortunately, as we have discussed above, there are many things that you can do to reduce the chances of being targeted by spam filters. Put these actions into practice and watch your ROI rises.

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