Silvestras from MailerLite

Silvestras9 min readTips and resourcesFebruary 13, 2020

How to avoid spam filters and reach the inbox

How to avoid spam filters and reach the inbox

Have your open rates suddenly plunged to single digits without warning or explanation? Don’t panic! Your subscribers still love you. They simply didn’t get a chance to open your newsletter. Why?

In 99% of these cases, your plummeting open rate is a result of your newsletter accidentally ending up in that nasty place we call the junk folder.

We know your newsletter is not junk. But unfortunately, it was flagged by a spam filter. This is a frustrating experience because there is not always an obvious reason why the filter put your newsletter into the wrong folder.

Your subscribers want to open your newsletter, but they need to receive it first. In this blog post, we will share some of the best ways to avoid spam filters when sending your emails.


Believe it or not, spam filters are your friend. Unsolicited emails, commonly known as spam, are a huge problem. There are over 200 billion emails sent on a daily basis and 59% of those are spam!

You don’t want all those bad emails competing with your valuable newsletter in your subscriber’s inbox. That said, spam filters are not perfect and often flag good emails.

A spam filter is basically a program that uses various criteria to determine if an email is spam. Some of these protocols focus on different aspects of the email such as:

Email header

Filters email headers that use false information.

Content filters

Looks for common words associated with spam.

Blacklisted addresses

Blocks all emails from known spammers.

User permissions

Email owners define specific rules to block emails they don’t like.

These are just a few of the ways that spam filters analyze your emails. The important thing for you is to do everything in your power to avoid these spam filters and end up where you belong—your subscriber’s inbox.

Here are 7 things you can start doing today that will help you stay away from that nasty junk folder.


Send newsletter from own domain

It’s perfectly fine to send emails to your friend or colleague from domains like @gmail.com, @yahoo.com, @hotmail.com, etc. However, when it comes to bulk email delivery, it is not a good idea.

You should always send newsletters from your own domain.

Why? Because MailerLite works closely with mailbox providers, such as Gmail and Yahoo Mail, to whitelist your domain or IP address. If you send bulk email from other domains, you are running the risk of sending your newsletters straight to the junk pile.

You should also avoid making frequent changes to your “From” field names, and don’t use strange names like “8wqq823o@yourdomain.com”. Use clear and reliable names like “newsletter@”, “support@”, contact@” or “feedback@”.

The best approach is to personalize your address using a real name, e.g. tom@yourdomain.com. 

Personalization is important in email marketing, in the guide below we'll explain why.

Authenticate your domain

Ok, you followed step 1 and added a personal email address like peter@yourdomain.com to the sender field. That is a great start. But before you push send, there is 1 more step to optimize your domain. It’s called Domain authentication.

Domain authentication is a method to legitimize your bulk sending domain with our servers so they can send emails on your behalf. This helps spam filters tolerate your bulk mailing and validates your domain.

We wrote a short guide on how to authenticate your email with MailerLite.

Check your newsletter content

As we mentioned earlier, spam filters are always checking your content. They don’t have the human ability to analyze words in context, so they basically flag any words or phrases associated with spam. If they find a spammy word, they are nastier than Chuck Norris.

While there are no magic keywords to improve your email deliverability, you can limit the use of risky words to reduce the chance of landing in the spam folder. 

Here are some useful tips to check your email for spam content:

  • Link only to legitimate sites with reputable domains. Check all your affiliate links to ensure they are above board.
  • Don’t go crazy with email length. Spam filters don’t like newsletters that are a mile long. There is not a perfect newsletter length. But if you have more than 200 words or the reader has to work hard to get through it, shorten it.
  • Balance your images and text. Spam filters see images as blank space. If you send a newsletter with one large image and no copy, they will consider it as an empty email and your days will be numbered.
  • Don’t use too many exclamation points!!!!!!!!!!!!!
  • Avoid writing text in red.
  • Make sure you are not writing in ALL CAPS. IT FEELS LIKE YOU’RE SCREAMING! Nobody likes that.
  • Avoid fishy phrases like “Please click here”, “Don’t miss this!”, “This is not spam!”, etc.
Never use purchased email lists

It is not just you. Everyone is tempted to grow their list by 100,000 potential customers by simply buying a list. If you are still considering this idea, stop!

Purchased lists are like ticking time bombs. Sooner or later they will destroy your reputation. Filled with non-existing email addresses and spam traps, they quickly inform mailbox providers that you like to break the rules by sending unsolicited emails.

Your messages will end up in junk folders. Even worse, you may be marked as a spammer.

To send an email using MailerLite, the recipient must be someone who has specifically asked to receive your emails by opting in or signing up in some way. If you are an online business, it can also be someone who has bought a product or service from you in the past 18 months.

When people unsubscribe from your newsletter it's always a little disappointing. However, it's important that you let people unsubscribe by offering a clear unsubscribe link in every newsletter (normally positioned at the end of an email). 

If you don't, you risk the chance that people will mark your email as spam because they don't see any other way to unsubscribe from your emails. So be a good human and make sure the unsubscribe link is part of your newsletter layout. It'll be worth it.

Turn unsubscribes into something positive

Surely, you'll end up with one subscriber less on your list, but you can give a positive twist to unsubscribes. When you add a survey to your unsubscribe page, you can collect feedback and takes notes on why people are no longer interested in your emails. With each unsubscribe, you now at least get the opportunity to improve your email marketing.

Your subject line is crucial for your open rate, but it's also an important part of reducing spam marks. People can take a quick look at your subject line and decide to mark it as spam. That's why we advise you to put some thought into your subject line. You can use the tips mentioned earlier (avoid all caps, fishy phrases and excess use of exclamation marks) to create a risk-free subject line.

In most cases, you'll be more than fine if your subject line is relevant and written with the reader in mind.

And for our last tip, make sure to keep a healthy email list with valid and engaged subscribers. How? By regularly cleaning your list using an email validation tool (we love MailerCheck). Doing this will make sure all invalid email addresses, like hard bounces, are filtered out of your list. A clean list will reduce the risk of spam trap hits and avoid your deliverability getting damaged.

Want to learn more about cleaning your list?

In this article, we'll explain how you can identify and remove email addresses that aren't doing your subscriber list any good. We'll also talk about the most common deliverability mistakes to avoid.


Follow the simple tips above and you will avoid most spam filters, stop your emails from going to spam and keep your open rate healthy. 

In the video below, Marcin will talk more about avoiding spam filters.

P.S. As a bonus tip, when confirming or greeting your new subscribers (e.g. via a welcome email), ask them to add your “From” address to their contacts. It is a clever way to bypass those spam filters. It never hurts to ask and it is highly effective.

Editor’s note: This post was originally published in January 2015, but has been revamped and updated for accuracy and comprehensiveness.

Silvestras Armonaitis

Hi, it’s Silvestras, a member of MailerLite’s customer support team. As the first remote employee to join MailerLite in 2014, I was the guinea pig to test if remote work was a good idea. Today, MailerLite is a remote-first company so the experiment was a success! To all the other remote workers who have joined since—you’re welcome.