Compare software
Find information

Press and News

<< Back


Email Marketing Tips for Avoiding Spam Filters

Even the most conscientious and forthright email marketer’s campaign can miss an important test. So, I’m here to help you prep for deliverability — the pop quiz no email sender wants to fail.

Hi! My name is Marie, I’m the Head of Customer Happiness here at SendinBlue, and I’m ready to stand in front of the class and share my report on Spam (and I’m not talking about the questionable canned meat).

Anyone with an inbox is familiar with the concept of email spam. The most blatant usually promises free limited-time gifts, miracle medical treatments, enlargement of certain parts, the ability to lose half your body weight, and so on. These obvious examples are pretty easy for email and internet providers to identify and block. But there are also more subtle versions of email spam that people would prefer not to receive, which is why Gmail, Outlook, Yahoo, AOL, and others have unique rules in place to block messages that they THINK might be spammy in nature.

Creating email campaigns that can pass the spam test each Email Service Provider (ESP) and Internet Service Provider (ISP) administers is the key to acing the email marketing game!

Lessons in Spam Filtering

ESPs and ISPs look at the following dynamics of all emails before determining if they’re worthy to pass:


User activity is measured to determine if most recipients find the emails that you send to be interesting and appealing. Positive engagement activities like email opens, clicks, and reads are seen as good indications and count in favor of the email. (The same way you get a good grade if you always have the right answer when called on in class). This is why it’s so important to segment your list and then target emails to appeal specifically to each segment! Targeted emails are more likely to have strong recipient engagement, boosting your credibility amongst ESPs and ISPs.


Low open rates don’t help an email’s case, but they also don’t count as strongly against an email as more overt activities like when recipients unsubscribe from emails or mark them as spam. (Think of this as the difference between falling asleep in class versus arguing with the professor before throwing a book at him/her – both are bad, but one is much worse.) These are blatant indications that users do not appreciate the emails you are sending and this performance does not endear you to ESPs and ISPs who are looking to deliver a good user experience. Ensuring that your email list is up to date will help you to avoid triggering a red flag with the most popular providers because you won’t be sending emails to people who have opted out of communications.

 Spam Traps

Spam traps are exactly what they sound like – email addresses created for the sole purpose of catching email spammers. (They’re basically the sneaky trick questions on the test meant to determine if you’re copying off your neighbor!) These addresses are never given out, so any emails they receive are being sent to them without their permission (either as a result of unauthorized sharing or email selling). Companies that fall for the bait are trapped into revealing their unethical practices and subsequently get punished by ESPs and ISPs with a ruler across the knuckles. Failing to identify and remove these addresses from your email list once they get on there can ultimately result in your company being blacklisted as a sender.


Every email that you send should have unique content because sending the same email to the same recipients repeatedly will irritate readers and cause your emails to be flagged as spam. (Think about how well it would be received if you submitted the same paper for every assignment!) You can certainly have a consistent email template, but you want to vary the message and the offer in each one so that it creates a unique experience for your recipients every time they open one of your emails. This not only helps you pass the spam test, it also provides an opportunity to test different types of content with your subscribers. Ultimately, this leads to better engagement.


Researchers publish long lists of the most commonly used words in spam emails.  These are basically considered the “bad words” of email. (And you don’t want to swear in class, do you?) Here’s a quick study guide of common types of words and phrases to avoid: 

  • Get rich quick (e.g. work from home, double your income, earn $, fast cash, home based, multi level marketing, cash bonus, etc.)
  • Unsolicited financial information (e.g. pre-approved, financial freedom, investment decision, mortgage rates, eliminate debt, stock disclaimer statement, etc.)
  • Abusing the word “free” (e.g.  FREE, free money, free leads, free preview, etc.)
  • Grammatical errors / exaggerations (e.g. 4U, $$$, f r e e, cents on the dollar, giving it away, etc.)
  • Pretending to know someone (e.g. Dear friend, Please read, Urgent, Congratulations, Information you requested, Winner, etc.)
  • Unsubstantiated health claims (e.g. all natural, lose, see for yourself, promise you, guarantee, weight loss, etc.)

To keep your emails from getting a bad rap, speak honestly to your readers and skip these types of words. 

Sender History

Unlike a student reputation that you can ditch every time you change schools, your sender reputation will follow you forever. Yes, even regardless of which email platform or IP address you use because it’s also connected to other elements of your sender identity (including your domain name). Once damaged, restoring your sender reputation is a time consuming and challenging process. That’s why it is so important to always follow email best practices!

Next Steps to Email Engagement

Now that you’ve learned more about what ESPs and ISPs are looking for, you’re ready to take on the challenge. These best practices will help you graduate to the next level:

Opt-In Only

Only send email to people who have opted into your emails. You can certainly invite your friends, family, and social followers to sign up for your emails, but never send emails to them without permission. And never buy, rent, or “borrow” email lists! That’s a sure way to be labeled as a spammer (and covered by spitballs in our class!).

Image Formatting

Don’t send emails that only contain one large informational or deal-focused image. It’s ok to include some words in your images, but be careful to incorporate actual text in your emails as well. This will keep your emails from getting blocked by ESPs and ignored by recipients who do not have images set to automatically download (or whose email clients experience an error loading your image).  It’s also important to use graphics strategically as some ISPs flag emails with too many images as spam.


Most people check email on their phones, so ensure yours are mobile-friendly! Incorporate responsive design in your templates so that content will resize automatically. Be kind to your recipients and ensure call-to-action buttons are large enough to be clicked by someone using a mobile device. (Tiny, unclickable buttons are a mean, mean trick.) Emails that don’t render well on mobile devices will often get ignored, deleted, unsubscribed from, or blocked.

With all of these lessons tucked away in your Trapper Keeper, you’re ready to ace the spam test! So study up, get a good night’s sleep, and then create an email marketing campaign that’ll pass even the strictest spam filters. The more spam-free email campaigns you create, the better your reputation will be and soon you’ll be sitting at the head of the class (while your competitors are sitting in the back row).

Happy Sending!

SendinBlue empowers businesses to build and grow relationships through email campaigns, transactional emails and SMS messages.
The platform combines a robust suite of services within a single, user-friendly solution.
1. Create beautiful responsive design newsletters thanks to a powerful intuitive editor
2. Segment your database
3. Schedule your sending. We take care of delivering it to the inbox of your clients.

SendinBlue Marketing Automation helps you communicate with the right people, at the right time and with the right message.

SendinBlue is powered by our world-class customer service team and offers pricing plans guaranteed to make you smile. SendinBlue launched in Paris in 2012 and now serves over 100,000 users in over 80 countries around the world.

More details of this software

Publisher press

> 05/02/2016 - 5 Best Practices for Using Email Merge Fields

> 26/01/2016 - Try the New SendinBlue Plugin for WooCommerce

> 11/01/2016 - Top 6 NonProfit Email Marketing Best Practices

> 25/11/2015 - Top 5 Resources for Customer-Centric Email Marketing

> 29/10/2015 - Interview (emailing): Amalia Bercot, Chief Marketing Officer – SendinBlue

> 06/10/2015 - 5 Resources to Turn Your Emails Into Conversion Machines This Fall

> 14/09/2015 - 5 Email Marketing Resources That Create a Winning Game Plan

> 03/09/2015 - Email Marketing Tips for Avoiding Spam Filters

> 09/07/2015 - How To: Warm Up A Dedicated IP Address

> 18/06/2015 - How to Keep Your Email List Healthy

> 08/06/2015 - Email Marketing Round-Up: May’s Top Reads