Email Marketing Campaign Gone Spam? 5 Tips to Avoid the Spam Filter When Sending Emails

If your emails do not reach the recipients inbox, they probably have been trapped by spam filters. Here are the 5 tips to avoid spam filter...

9 Oct 2019 21150 Views

Written by Natalia Theofilopoulou

As the number of email users is constantly growing, online communication has become an every-day routine (1,2). As an internet marketer, you can use email marketing in order to expand the customer reach, create personalized communication, improve the relationship with your consumers and quickly measure the return on investment of your campaign (2,3,4,5). Email marketing is cheap or even free, easy to access and actually still very effective (1). Either you work for a big, medium-sized or small company, if you manage to create a successful email marketing campaign, you can achieve not only a steep growth on online and offline sales but also a higher brand loyalty (1,4).

But for doing so, your emails need to reach the Inbox folder of your targeted consumer. Is that given? The answer is no. One out of every five commercial emails ends on the Spam folder of the recipient or is entirely blocked (7). You can find below 5 tips that will help you avoid the spam filters and increase your email deliverability.

What exactly is spam?

The term “spam” is used to characterize an unsolicited commercial e-mail (UCE). It is defined as “the practice of indiscriminate distribution of messages without permission of the receiver and without consideration for the messages’ appropriateness” (8). In other words, any bulk commercial email communication to which consumers have not consented can be described as spam (9).

The increasing use of email marketing has created a dramatic growth in the number of unsolicited commercial e-mails (10). More than 70% of the emails sent globally are identified as spams (11).

What is the spam filter and how does it work?

Spam filter is an automated mechanism that identifies whether an email is spam or legitimate. Once the spam filter recognizes a junk mail, it prevents its delivery to the recipient’s inbox. (11,13).

There are two main types of spam filters:

  • List-based filters: They categorize senders as spammers or trusted users. If the sender is recorded as a spammer, the filter blocks the delivery of the email.
  • Content-based filters: They identify words or phrases included in the email and define whether the message is spam or legitimate. They are more effective than list-based filters. (11)

How to avoid spam filters? Five tips

According to ReturnPath, only 79% of the emails sent by marketers reach the recipient’s inbox folder. The reason is that spam filters become more and more rigorous. Even a small mistake of you when sending emails can trigger the spam filter and prevent your message from delivery (14). Here you can find 5 tips to avoid the spam filters and increase your email deliverability.

1. Present your identity

First and foremost, when trying to reach customers, your email address should preferably include your personal name. Avoid using impersonal or generic email addresses, such as 1234abc@domain or no-reply@domain (14). In addition, instead of having the name of the ESP in your email address, such as or, choose to add the name of the brand or company you are working for.

An example of an optimal email address is yourname@company.

It is important to present clearly your identity so that customers can easily recognize you. According to a study by Convince and Convert, 43% of email recipients forward emails to the spam folder exclusively by evaluating the name and the email address of the sender (14). Hence, if recipients cannot understand that the sender is you, they might probably mark your emails as spam even if they would have been interested in your content (17).

For the same reason, avoid making changes in your email name or address (14). By changing your “from” details, you will confuse recipients, you will become less recognizable and you are more likely to be marked as a spammer (16).

2. Have a clean recipient List

Having a clean contact list is not limited on what the General Data Protection Regulation (GDPR) requires. Apart from having the explicit consent of subscribers to receive emails by you (19), you should try keep your email lists clean by deleting inactive or dormant subscribers (14).

Every time you receive a delivery failure notification, simply remove the invalid address from your contact list. In addition, you should regularly evaluate whether the valid contacts open, read or click on your emails (14). There is no point in continuing sending emails to subscribers who are not interested in your content (20).

Continuing sending emails to these invalid or dormant accounts increases the bounce unsubscribe rate of your campaign. This can damage your reputation as sender and immediately alert the spam filters (14).

3. Content is the king

Maybe the most important factor that influences the deliverability of an email is its content. For this reason, as an internet marketer, you have to focus on producing engaging content and providing your subscribers with useful, fresh and interesting information (2,16).

In addition, instead of sending mass emails, you should define and address your target market (16,22). Evaluate your email reports, find the most appealing topics and prepare more relevant emails for the people you want to reach (17). The more valuable and customized the content is, the higher the engagement of recipients will become (23). According to analysts (23), emails with personalized subject lines are 22.2% more likely to be opened.

On the other hand, if your content is irrelevant or less personalized, customers will probably transfer your emails on the spam folder (17), which will trigger the spam filters and affect your IP reputation.

4. Don’t break promises

Before asking customers to subscribe, provide them with a clear image about the content and the frequency of the emails you are going to send. And after having their consent, just be consistent. Do not provide them with different information of the one they expect to receive by you (17). And do not contact them too frequently if your opt-in form “promised” occasional updates (20).

Breaking your promises will damage your reputation. It may impel customers to unsubscribe or mark your email as junk. Try to build a truthful relationship with your customers and fulfil their expectations, so that you avoid being recognized as spammer and blacklisted by spam filters. What else can you do and how to avoid emails going to spam?

5. Take care of the details

Spam filters scan your email copy rigorously and can be alerted by small details that you need to take into consideration. More specifically, big images that increase the loading time or do not display correctly should be avoided (14). Spam filters can easily identify these technical issues and mark your email as junk. In addition, avoid sending emails that include only image (23). Ideally, prefer a low image-text rate and let images occupy 30-50% of your whole email content (26).

Similarly, it is better not to include embedding forms and attachments in your email. They are usually not supported among common email clients and, as a result, are recognized as security risk by spam filters (14,23).

When sending links, you have to be careful about the reputation of the domain you redirect the recipients (16,20). Instead of using any link shortening services like (16,20,23) that make your email look spammy, you should send the full URL. Finally, you need to ensure that the URL functions properly (23).

It is also very important not to contain any spam trigger words and phrases in your emails. Which are they? All the salesy and appealing words, such as “free”, “money”, “best price”, that immediately alert the spam filters (14,23,26). You should also exclude using different font sizes, colors and exclamation points that make your email suspicious both to recipients and spam filters (14,20). Finally, be careful with the spelling and grammar rules because these type of errors make your email appear unprofessional and spammy (14,23).


These are some main tips that can help you avoid spam filters when sending emails. However, they cannot guarantee that you will achieve 100% email deliverability. By following these tips, you are more likely to increase the deliverability rate, preserve your credibility and reputation as sender and reduce the possibilities of being marked as a spammer (14). High quality content targeted to the right audience in the right way can be a key factor for a successful email marketing campaign and a higher brand equity.


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Students from the International Marketing and Brand Management program at Lund University are the contributing authors for the BrandBase blog.