The complete guide to avoiding being marked as spam

Jun 14
9 min read
When you do email campaigns regularly, one question often comes up. How to avoid your emails being flagged as spam? We help you answer it!
Garbage bin with papers - Photo Steve Johnson on Pexels

How to avoid your emails being flagged as spam? This question is important since spam filters are constantly being updated.  Email clients are also evolving. Especially since Gmail now classifies promotional emails in a separate category.

Let's discover best practices together. To get through those anti-spam filters and reduce the rate of reporting as spam by recipients.

SPAM: definition and reporting

Spam is unsolicited electronic communication, largely by email. You might think of it as unwanted email or junk mail. It's generally a question of sending large quantities of mail for advertising purposes.

Spam is an unsolicited and unwanted communication. There are 2 ways to identify an unwanted email:

  • The classification as spam is automated by the anti-spam filters of the email reception servers (Gmail, Yahoo...) and email clients (Mail, Thunderbird, Outlook...).
  • Reporting as spam happens manually by the recipient by clicking on the "report as spam" button. This report is then forwarded to the receiving servers, email clients, and sometimes even to the routers in charge of sending. Reporting by recipients feeds into and improves spam filters.

Part 1: How to get past spam filters

Anti-spam filter illustration

Spam filters

Anti-spam systems evaluate each email according to a variety of criteria from which they calculate a score. If this score is too high, your email will be marked as spam. The goal is to look as little like spam as possible from the filters' point of view. Here are the essential practices that will allow your emails not to get flagged as spam.

1. The sender name and the subject of your email

The sender - subject pair is the first thing your recipients see of your email. The email open rate depends on the trust they have in the sender and the interest they have in the subject. That's why spam filters are vigilant on these 2 points:

  1. Use the same sender name for each email to capitalize on the trust acquired with your recipients. Spammers tend to change it in order to fool their targets. So be consistent but also authentic by using the name of your company, your brand, or a person.
  2. As for the subject line of your emails, avoid words associated with spam such as: free, offer, promo, urgent, 50%, win, $, price... Do not write your subject line in capital letters. Do not use exclamation marks repeatedly. Finally, write your subject line so that people want to open it. But be careful not to stray too far from the subject of the email content.

2. The content of your email

Indicate your physical address so that the spam filter validates your authenticity. This is a practice that has become mandatory in many countries, and it's a way to show your credentials.

Immediately abandon the idea of using a single large image for the content of your email. Spam filters can't read images. They assume you are a spammer trying to get around them. Instead of designing your email on Photoshop, use your email tool's editor. It's specially designed for this purpose.

The image to text ratio is an important factor in evaluating your email. So don't use too many images in your email content. Remember that many email clients (especially for professionals) don't display images by default. Finally, take care to insert an alternative text to all your images.

Be sober in the formatting of your email. Spam filters don't appreciate a multitude of colors. Or the overuse of bold, italics, underlines, etc.

Avoid using subjects or formulations that are immediately associated with spam. The SpamAssassin service recommends avoiding topics related to: an incredible discovery, a guaranteed refund, an emergency, a lot of money... In short, avoid all promises that sound too good to be true.

Never include attachments in a mass email. This is a practice that is very much frowned upon by anti-spam filters.

Anti-spam filter illustration

3. The unsubscribe link.

An email that doesn't contain an unsubscribe link is considered suspicious by spam filters. It's mandatory. Don't try to hide it, on the contrary, make it visible (yes, yes). It is less serious to lose a few subscribers than a majority of them receiving your email in their spam folder.

4. The code of your email (for the more technical)

Use quality HTML code. It's very important that the receiving servers and email clients can read your email correctly. It's essential to respect the HTML standards for email. For this, don't hesitate to trust the templates proposed by email tools.

Do not use HTML code imported from Microsoft Word for your email. This code is not at all adapted to email clients.

Do not insert Flash videos or javascript in the content of your email.

Do not neglect the text version of your email. This is what recipients will see if their email client does not allow the HTML version to be displayed. Maintain a high level of fidelity between your 2 versions.

5. Reputation of the IP address and the sending domain

When spam complaints are sent to the servers of Internet Service Providers (Orange...) and webmails (Outlook, Gmail...), they share them between each other. These complaints feed blacklists of domains and IP addresses now considered spammers. Your objective is to avoid having your domain and sending IP address blacklisted.

Be careful when choosing your sending domain. Check if it's not blacklisted. Do the same with your sending IP address. The sending IP address will most often be that of your email solution.

“If you send a campaign and it causes a high SPAM complaint rate, our IP addresses may be blacklisted by the receiving servers (Hotmail, Gmail...). This prevents our customers from sending to the addresses of the operator in question."

Serious email routing solutions, like Cakemail, watch upstream and act downstream. This maintains a good reputation for all its IP addresses.

"We are very careful about the reputation of our IP addresses. We make our customers aware of the challenges of email. And we actively monitor our customers' sending statistics to identify any suspicious behaviour. When one of our IP addresses is blacklisted, we work with the email server involved to resolve the situation.”

The choice of your email marketing solution is quite important. Choose one of the most reputable email marketing companies. 

Part 2: How to avoid being reported as spam by your recipients

Report as spam

How to prevent your recipients from clicking the "report as spam" button? Here are 4 main principles you should apply in your email marketing strategy.

1. Always ask for your recipients' consent before sending them an email.

If you remember only one thing from this article, remember this: never send an email campaign to someone who has not explicitly given their consent to receive it.

A sale or a registration on your site doesn't mean someone's agreed to receive promotional emails. Do not send promotional emails to your customers (or users) who have not explicitly given their consent. Create a specific mailing list (ban sending to your entire base). When signing up, highlight the benefits your customers could receive (discount codes, free white paper, etc.).

A business card left at a trade show or conference doesn't mean that you've agreed to receive promotional emails. Contact your leads manually by inviting them to subscribe to your newsletter.

Banish any notion of buying or renting email databases. Most of the time these databases contain unused or deleted addresses. This is a prohibited practice. Don't waste your budget on buying email databases whose recipients never agreed to receive your email.

Don't sell or rent your email database either, especially if you intend to use it to develop your business. You will lose some of your recipients with this method. That's a much bigger problem than the little income you might get from it!

2. Keep your recipient lists healthy

Implement double opt-in, systematically. Each new subscriber must confirm their subscription. Confirm by clicking on the link in the message they receive. While this practice adds a step for the subscriber, it allows you to build a highly qualified email base. Complete with verified email address owners. The likelihood of your emails being classified as spam is reduced. Subscribers have demonstrated their interest by going through the process.

Clean up your mailing lists regularly. Delete email addresses from  which you receive spam complaints. Also hard bounce notifications, indicating that the address no longer exists. Consider manually unsubscribing recipients immediately upon request.

Set up several mailing lists using the data you have on your recipients (gender, age, interests, purchases...). This will allow you to better target your recipients. Recipient's who'll appreciate receiving personalized emails. They will be less likely to report your emails as spam.

3. Manage your sending frequency with respect

Adapt the frequency of your sendings according to the profile of your subscribers. This limits the spam rate. State during registration how often you'll be sending email and what they should expect from your newsletter. Propose several reception frequencies at registration or in your unsubscribe form.

Do not let too much time pass between the moment you collect an email address and the moment you send your first message. Don't risk your subscribers reporting you as spam because they simply forgot about you.

4. Highlight the unsubscribe link

Yes, you read that right. I'll even insist on putting the unsubscribe link at the top of your email. If your subscribers don't want to receive your emails anymore, they look for the easiest way to unsubscribe. If it's easier for them to click on the "report as spam" button than to click on the unsubscribe link, they'll do it. Even if they don't actually consider your email as spam.

And the spam reporting loop is closed

We know that some of you will be reluctant to put these tips into practice. Remember: a recipient reporting your email as undesirable informs his email client and his receiving server. Manual filtering feeds into the automatic filtering systems. It can lead to your domain being blacklisted if many of your recipients do this.

The fear of missing out on short-term opportunities shouldn't make you lose sight of this important fact: it's far more important to maintain a good reputation on the web.

Consent from your recipients, up-to-date lists, and a respectful sending frequency are the keys to the success of your email marketing strategy. Take action now to avoid finding your way back to the spam folder.

Bonus: Did you know that the word spam originates from the name of a brand of pre-cooked canned meat? The association with the word spam was popularized by Monty Python fans who parodied an ad for the brand in the late 90s.

Monthy Python Meme - Image from Chapman Project on
Monthy Python Spam sketch has led to many memes!

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