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22 Tips to Help Online Marketers Avoid Spam Filters

22 Tips to Help Online Marketers Avoid Spam Filters

I am writing this post the same week that I had a small (metaphorical) heart attack. The money is in the list (well, sort of, but more on that later), so when I received a notification alerting me that my email sending capabilities were locked, I panicked. I assumed the worst. I was told I used a phrase that would trigger spam filters.

“I…am…a… spammer,” I thought to myself.  

I was only a few typos away from being no better than that Nigerian astronaut lost in space. You know, the one who needs you to Western Union $3,000 to help him pay for a Soyuz return flight to bring him back to Earth BUT will pay you a huge (unbelievable huge actually) portion of his “flight pay” money (plus interest) that he has racked up while floating around up there aimlessly in space.

I felt like that guy…

Convertkit Account locked

Well, I over-reacted a little bit. My account was unlocked that same day.  

I was told that my line selling a “money back guarantee” was, ironically, commonly used in SPAM emails.

While I did contest with the support team at Convertkit that their parameters were a bit tight, I was relieved to know it wasn't a bigger issue.

As nervous as I was at first, I’m glad that this happened because it was an eye-opener for me. After this happened, I did a lot (a LOT) of research into what constitutes SPAM and how we can make sure we don’t inadvertently send out emails that are triggered as such to our loyal email subscribers.

What is a Spam Filter?

A SPAM filter is a program that ensures recipients don’t see emails that may be irrelevant or malicious.  

Simply put, they prevent junk mail.

Large email providers like Gmail have these systems built into them while some others may be added manually by the user.

It is important to understand that SPAM filters aren’t perfect.

I am not going to teach you how to “game” SPAM filters in this article, but how to ensure you don't accidentally do things that will get your well intentioned emails labeled as SPAM. If you are reading this in an attempt to learn how to send SPAM and not get caught, go away. Thanks.

Our intentions aren’t interpreted by computers, so as email marketers, we need to craft our emails accordingly to prevent being flagged as SPAM, fair or not.

The best practices in this post are written understanding that these filters are programs, not people. Our intentions aren’t interpreted by computers, so as email marketers, we need to craft our emails accordingly to prevent being flagged as SPAM, fair or not.

How Spam Filters Detect Spam

There are many different criteria involved in a spam filters (and the number is ever growing).

Here are some of the more important ones.

  • Reputation (IP Address and sender domain)
  • Relationship (how you connected with subscriber)
  • Quality of content (including subject line)
  • Quality and safety of links in email
  • Inclusion of text version of email
  • Images (how few or how many)
  • Ratio of images to text

It is important to note that SPAM is relative to the recipient. Here are some of the subscriber actions that affect whether a recipient will continue to see your email or if it will go to their SPAM folder.

  • Whether they open your emails or not
  • Time spend reading your emails
  • Whether they scroll to the bottom of email or not
  • Whether they display images or not
  • Whether they mark emails as SPAM (duh)
  • What tags and folders a subscriber puts your emails into
  • Whether they forward your emails
  • How many times they open the emails

Tracking all the different criteria mentioned above (and more) allows for spam filters to create complex ranking formulas. Along with weighted spam factors, these criteria are added to determine an email score for each recipient.

# 1 Don't add everyone from your general contact list

Just because you have someone’s email address doesn’t mean they want to hear from you regarding your business OR that you deserve to promote to them.

Never buy an email list#2 Don't buy or rent an email list

Anyone who has ever grown an email list organically knows how tempting it may seem to just fork over some cash to have access to a huge audience.

#3 Don't scrape websites for email addresses

It goes without saying that this will only get you in trouble. Do this, and you'll probably end up on blacklists.

#4 Craft quality subject lines

According to a study by Hubspot, 69% of people mark their emails as SPAM simply based on the subject line! Create curiosity and deliver on it, don’t use clickbait and annoy your readers.

#5 Use clean coding

My emails have no fancy coding. They are simple and personal. I have found adding too much to them hurts my list in terms of unsubscribes and low click rates.

#6 Use Professional formatting

CAPS LOCK, dozens of exclamation points, and wild colors should be avoided. I am guilty of using all caps at times on one or two words for emphasis, but bold or italics will do the trick most of the time.

Never use Red or white font! Those are triggers for SPAM.

#7 Avoid spammy words

There are a ton of words that are “hot” for spam filters. Don't mention getting rich quick or making tons of money or getting free everything today. Definitely never include anything about a “Money Back Guarantee.” I learned that the hard way.  

#8 Have a sound “link to text” ratio

From a marketing perspective, you don’t want to have too many calls to action in one email anyway (I try and have no more than one per email), but from a SPAM perspective, you really need to be careful not to overdo it with links.  

#9 Have a sound “image to text” ratio

Since spammers want to avoid using the hot SPAM words, they will often use a high number of images,  (because the words on them aren’t readable by email filter). This means we need to be sure to not have too many images relative to the text.

Also, be sure to send images that are not overwhelmingly large. I recommend keeping your images under 50 kb if possible. Use a tool like tinypng.com for this if your email provider doesn’t have an integrated system.

Understanding the CAN-SPAM Act 

The CAN-SPAM Act is a US federal law passed in 2003 that sets the rules for commercial email. Fines can range as high as $16,000 per email that violates the law!

Here are the general takeaways of the CAN-SPAM Act.

  • Don’t deceive your reader. You should never use deceptive subject lines, reply-to addresses, from-names, or call-to-actions.
  • Unsubscribing needs to be easy. You are required to include an unsubscribe link in your emails and it must stay live for at least 30 days after sending. You will also need to remove unsubscribes within 10 days of opt-out. I use ConvertKit, and it does this all for me.
  • You must include your real mailing address. This is your physical mailing address, not just a vague location.
  • You can never send without consent. As we discussed, email only those people who expressly opt-in to your list.


#10 Use a human reply-to address

Don’t use something like “do-not-reply@yourrudecompany.com.” I find it ironic that companies want you to listen to them, yet they don’t want to hear from you!

Never use a standard email like “@yahoo.com.” Be sure that you have a business email @yoursite.com or @yourcompany.com.   Why is this? These email providers tell each other to!

#11 Use descriptive text instead of URLs as link text

Don’t use long direct link URLs, but, instead, put the URLs behind text.



Hide your links behind text...

#12 Don’t wait to start sending emails

The money is NOT “in the list,” it is in how you use it. If you fail to connect with your subscribers early and often, they will be surprised when they hear from you way down the road and may even mark you as SPAM since they don’t remember how they got on your list.

#13 Be consistent

Just as with sending emails early to ensure you connect right from the beginning, you need to have some regularity in the frequency of your emails to ensure you aren’t forgotten and accidentally marked as SPAM.

#14 Purge your old, inactive subscribers to avoid spam traps

ISPs can convert old, unused emails into “honey traps” or SPAM traps. As long as you are building your lists ethically and not scrapping them, you will be fine.

#15 Include a text version of your email

HTML code is easier to conceal bad calls to action. It isn’t mandatory, but including a text version of your email will not hurt.

#16 Use a reputable email service provider

I use ConvertKit and have had no problems.


#17 Use a double opt-in

Although they will lead to a smaller number of sign-ups per day, double opt-ins have a number of benefits.

First, double opt-ins will protect your list from bots and will filter your list to only real people. Remember, real people who consent with real intent will be your real buyers.

With a double opt-in, you can also save things that will allow you to prove you are not a spammer in the event that one of your subscribers claims you are.

#18 Segment your list to provide relevant emails

If you have multiple “niches” inside of your list, be sure that you separate them. All of your subscribers don’t need to see all of the same emails. Keep the emails as relevant to each reader as possible.

#19 Don’t forget to use spellcheck

Spelling is not something that goes unnoticed by your readers. According to that Radicati Group study, 80% of all respondents find spelling and grammatical errors to be the most unacceptable email offense.

If that isn’t bad enough, typos are also SPAM triggers.

#20 Use the recipient’s name

While I have always found this corny and insincere, including the recipient's name will help alert the SPAM filters that you do in fact know the person.

I made the mistake early on of not collecting first names. Do this from day one in your opt-in forms! You will be glad you did later.

#21 Use alt text with your images

Many mailboxes are programmed to block images by default. This means your message can be lost if the recipient opens your email and doesn’t see the point of it without these pictures. Alt text clarifies what the reader would be seeing a bit.

#22 Keep your emails short

Long form copy can trigger SPAM easily. Readers also appreciate this. If you need to use a longer copy, be sure that you break your content down into paragraphs and include images for breaking parts down.


Avoiding SPAM filters is not as difficult as it seems. Besides things like hot words (that may trigger false positives) and using too many links/images, building your list ethically and sending only quality content to people who have expressly asked for it will keep you in the clear.

About the author

Nate McCallister

Nate is the founder and main contributor of EntreResource.com. He is a lifestyle entrepreneur who spends his time building businesses and raising his two kids Sawyer and Brooks with his beautiful wife Emily. His main interests include copywriting, economics and piano.

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