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How to avoid the email spam folder?


Avoiding the spam folder is a constant battle for email marketeers. Lose the fight and your message will be lost. So, this is an important topic to pay attention to.

Broadly speaking, issues to watch out for when trying to avoid the spam folder, fall into three sub-categories:

Technical, Legal and the Message content:

Technical Spam Issues

There are numerous “behind the scenes” technical issues that anti-spam filters look for.  Some of the most common are:


    • Sender reputation – has the email server IP address been used to send email that has been identified as a likely spammer?
    • SPF and DKIM records – used to verify the sender is who they say they are.
    • When the emails are sent – during normal hours?
    • Individual users marking the email as spam.
    • Sending to dead / invalid email addresses.
    • Low open rates.
    • Not respecting unsubscribe requests.
    • A real reply address should be provided.
    • From name should be something familiar, the company name, product name or a person. Once chosen, stick to the same name.

Where we can, Marketwise takes care of these issues for our customers. 


Legal Spam Issues

The various global anti spam / privacy rules have some common themes:

    • Unsubscribe option must be provided.
    • A physical office address must be listed.
    • Content must not mislead.
    • Content must be relevant to the recipient.

We will ensure that technical and legal issues are taken care of. You as the content owner, are freed to focus on creating great content.

Subject lines that pass the spam filter

As discussed in our Improving email open rates page, the subject line is critical to your email campaign. It can literally make or break your campaign.  Let’s list out a few absolute howlers, that are sure to accelerate your path to the spam folder.


    • Overuse of CAPS.  The safest format is simple sentence capitalisation, ie the first letter only.  Subject lines like “LAST CHANCE to register for the webinar” may not perform well.
    • Emojis cool. Although popular with younger folks, for professional, business communications, they are often frowned upon. One maximum, but we would recommend A/B testing to see the result with and without the emoji.
    • Excessive punctuation!!!! Keep it simple and professional. Marketwise recommends zero use of !?$£€ and other unusual characters.
    • Avoid certain keywords. These are typically money based or overhyped sales words. Generally avoid words such as: Cash, Free, Cost, Credit, Join, Amazing, Great offer, Guaranteed, Risk free.

The subject line is absolutely critical, keep it simple, enticing, honest and relevant. 

If you want to try anything a little unusual, A/B testing is always the best option.

Message content that passes spam filters

All of the guidelines for subject lines apply to the message body also.  Our core recommendations for great message bodies is on this page. Additionally, keep the following in mind to avoid the spam folder:


    • Overuse of images.  Keep the amount of images low, compared to the textual content.  Usually a simple banner / branding image and perhaps one more lower down is sufficient (but of course it depends on the email length)
    • Keep your content brief and to the point, our blog post on brevity is a great guide.
    • Use of the “alt=” html tag. Images should always have an “alt” tag defined in the html for every image. This will be displayed if the image cannot be fetched. If it is missing, your spam rating will increase. We don’t recommend alt=””, it is always better to put something, “.”, “-” or some other small character.
    • Avoid javascript embedded in the html. This is often blocked not by spam, but by security filters, but the effect is the same (or even worse).
    • Avoid embedded forms. Again, these can be perceived as security threats / phishing attacks and should always be avoided. Your call to action should be a simple link to your landing page.
    • Test. Several online tools are available. Mail-tester has a nice interface and allows 3 free tests per day, enough for occasional users.


The key, as always, is relevance and building trust with your reader so they are more likely to add you to their address-book.

It should be noted that the anti-spam industry is constantly evolving and improving the way it detects spam. What works today, might not tomorrow.

A well written, relevant message without hyperbole, will always stand the best chance to get through an anti-spam system unmolested.

Avoiding the spam email filter

Related Blog content

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Blog: Anatomy of the Perfect message

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Blog: How to be Creative!

FAQ for Email Marketing


Is email marketing worth it?

Many studies have shown a great ROI for email marketing, averaging at a 30x to 40x return. The key is to use high quality data and send relevant, engaging messages. We can advise.

How do I target email marketing?

Build your ideal audience. Based on what market segment they work in, what they do and what they specialise in. Add in geographic location and you have a well targeted email list. Now you need to send relevant and interesting messages to build trust.

How do I improve email open rates?

Two main factors. The subject line and email deliverability. The subject line should be short, create some intrigue or curiosity and avoid spammy words. You build trust with an audience over time.
Email deliverability depends on good email data and a good email reputation.

How do I improve my CTR?

Some quick tips are:
Keep your message short, to the point and easily skim-able.
Be relevant and create curiosity in your audience
Have a single Call to Action button with a clear message on it "Download the report".

What is A/B testing?

This simply means testing two versions of something. Most common is Subject Line testing. Send out two different versions and see which gets the best response. Testing message content is possible as well. Ensure you only change one thing, so you know what made a difference.

How can I avoid the Spam filters?

Two main causes:
1. Technical reasons, poor email reputation and lack of email authentication.
2. Message content is spammy. Cut out flowery language and keep it professional.

What is contact nurturing?

This simply means sending multiple messages over time, to build up trust and a stronger relationship with your audience. Its rare to be able to send a single message and expect a brilliant response. Build trust with a series of engaging messages.