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How to Avoid Spam Filters in Email Marketing

September 1, 2020

You designed what looks like the perfect email campaign. It has a catchy subject line, the design looks clean, the text is engaging, and there’s a clear CTA. But, is there still a chance your email marketing campaign could be caught by a spam filter?

We’ll cover everything you need to know about avoiding spam filters in this guide, including:

  • What is considered spam?
  • Why spam emails are bad
  • What affects email deliverability
  • How to avoid sending spam emails

With spam messages accounting for about
54 percent of email traffic, you don’t want your next campaign to be part of that number. Don’t worry: We’ll get you on the right track so you don’t become part of that statistic.

What is spam email?

An email is labeled as spam if it is both unsolicited and a bulk email (ex. newsletters, customer communications, etc.). 

Let’s break that definition down even more. An electronic message is spam if:

  1. The recipients’ personal identity and context are irrelevant because the email is equally applicable to many other potential recipients.
  2. The recipient hasn’t verifiably granted deliberate, explicit, and still-revocable permission for it to be sent to them.

Now that you understand what we mean by spam email, we’ll show you why it’s important you aren’t sending this type of message.

Why spam can be a pricey mistake

Besides wanting to offer your audience valuable content that’s targeted to them, another important reason you shouldn’t send spam messages is because they could cause you to be noncompliant.

The Controlling the Assault of Non-Solicited Pornography and Marketing Act of 2003 (CAN-SPAM Act) was created to protect consumers from spam emails. And brands who aren’t in compliance can face up to $43,280 for each separate email in violation.

Thankfully, the rules in the CAN-SPAM Act are pretty easy to follow once you get your email template set up. Here are the main requirements:

  • Include an opt-out mechanism (ex. unsubscribe link)
  • Identify the message as a solicitation or advertisement
  • Include the sender’s (company) physical postal address
  • Don’t have false or misleading header information
  • Don’t use deceptive subject lines

Incorporating those elements will help you stay compliant and out of spam filters.

What affects email deliverability

You want to give your audience every opportunity to read your amazing email campaign. And that starts with making sure the email is delivered to their inbox — which is called email deliverability.

  • Email deliverability is the rate at which your email makes it into recipients’ inboxes.

That rate goes down when an email bounces or gets automatically filtered into a spam folder. Some marketers like to use email deliverability to gauge the likelihood of their email campaigns reaching their subscribers’ inboxes related to actual delivery (ex. bounces, throttling, bulking, ISPs, etc.).

Sending reputation

There are several factors that can play a role in keeping your emails from reaching their inboxes, including your sending reputation (aka sender score). The sender score assigns a percentage to the likelihood of the sender using email marketing best practices. 

That score includes things like:

  • Clean email lists
  • Complaint rate
  • Sending volume
  • Message filtered rate
  • Sender rejection rate
  • Unknown user rate
  • Spam trap hits

Sender scores are based on a scale of 0 to 100 (with 0 being the worst), and a score is assigned to each IP address you send from. You can find your sender score for free from services like

So, why does this score matter?

Well, ISPs use sender scores to determine whether an email belongs in the inbox — or the spam folder. The higher your score, the better your email deliverability will be for your campaigns.

By keeping your reputation high and staying compliant, you’ll not only have a better chance of landing in their inbox — but that will also help you improve your ROI.

Ready to learn how you can improve your email marketing strategy to avoid spam filters? We’ve put together an extensive list of ways you can help your emails hit their inboxes.

38 ways to avoid the spam filter

Now that we’ve covered some of the basics of email deliverability and why you want to avoid sending spam of any sort, it’s time for the main event. Here are 38 ways to make sure your email marketing campaigns avoid the spam filter.

1. Only send emails to people who have opted into your list (well, sort of). 

Known as permission-based email marketing, this technique ensures your audience wants to receive your email messages. 

But, what if you use to capture contacts who visit your website (i.e. email-based retargeting) and aren’t currently your subscribers? Great question!

  • We only capture leads in the United States who are on the opt-in list, so no legal worries there. And as for avoiding the spam filter if you reach out to these emails, it’s best to start with an immediate welcome series. That way, you reach them as soon as they hit your site, and you give them a way to unsubscribe if they so choose.

Here are more email-based retargeting best practices:

2. Use a double opt-in approach.

When someone signs up for your email newsletter on your website, for example, you send them an immediate email asking them to confirm their subscription by clicking a CTA or following a link. That helps weed out any inadvertent signups, potential errors, or unauthorized uses of email addresses. 

It also reminds the user they signed up for your list (us humans forget things easily), and it kicks off what we hope will be a long-lasting relationship between them and your brand.

3. Stop emailing addresses that have repeatedly bounced.

When an email hard bounces, that means there’s an invalid, non-existent, or closed email address. These emails will never be successfully delivered, and these addresses should be removed.

A soft bounce, on the other hand, is when an email gets as far as the recipient’s mail server but bounces back undelivered before it makes it to their inbox. That can be caused by factors like:

  • Inbox is full
  • Email size is too large
  • Server is down

Your email service provider (ESP) should flag any soft or hard bounces, so you’ll want to make sure to remove these addresses from your lists as needed: Always remove hard bounces, and remove soft bounces if they continue.

Considering bounce rates are one of the key factors looked at to determine your sender score, you want to make sure you reduce the number of bounces you have.

4. Regularly clean up your email list.

Contacts go cold. It happens to even the best of marketers. So, make sure you’re regularly cleaning out your lists to remove anyone who hasn’t engaged with you in a while. Sure, it might hurt to think about reducing your list size, but they are only bringing your email marketing metrics down — and possibly increasing your chance of being caught by the spam filter.

Before you cut your delinquent addresses, you can first try to get them back with a re-engagement campaign. You’ve seen what we’re talking about. They have subject lines like, “We miss you,” and “If we don’t hear back from you…” Then if they don’t engage, you’ll know you gave it your best effort and can move on. Sometimes, it’s not you, it’s them.


See what we did there? But back to the point: Don’t do that. You shouldn’t use all caps in your subject lines or in your email copy. No one wants to be yelled at, and using all caps can rub people the wrong way. It can seem spammy and annoying. The vast majority of recipients have even said they prefer an all-lowercase subject line to one in all caps.

There are other ways to get your message across. You can:

  • Personalize the subject line and email copy 
  • Use engaging language
  • Provide content that’s relevant and valuable to the consumer. 

Just don’t resort to the gimmick of putting it all in caps. You’re not helping anyone.

6. And don’t use exclamation points!!!

Sorry, we couldn’t resist. Just like using all caps can be a spam signal, so can exclamation points, especially several in a row. When nearly 70 percent of email recipients say they report spam based solely on the subject line, you better make sure yours doesn’t catch their attention for the wrong reasons (like using exclamation points).

Let your content speak for itself. If the words aren’t strong enough to stand without an exclamation point (or all caps), chances are it’s not very good. So, figure out another way to get your message across.

7. Heat up your IP.

If you’re new to email marketing, your IP address is going to be cold — meaning you are an unknown sender at the moment. Because of the countless spammers who change addresses constantly, cold IP addresses are guilty until proven innocent.

So, you’ll need to put in a little work to make your IP all warm and toasty. Do that by sending emails to a group of dedicated contacts — the ones you know will want to read your newsletters and other campaigns. These are your most engaged customers who are sure to open and click-through. Then, build up your sending list from there until your email marketing becomes more established. You can’t run before you walk.

8. Don’t send attachments.

We’re sure you have tons of amazing PDFs and other files you’d like to share with your audience. But attaching those files to an email isn’t the way to go about it. Most email servers aren’t going to allow attachments, anyway.

Instead, include a clear CTA that links to the content, along with a description about what they will find if they click through. This is a great way to get them to your landing page with a lead magnet so they will convert.

9. And don’t send media.

Along the same lines as attachments, you also want to steer clear of videos, Flash, or JavaScript inside of the email. Most email providers aren’t going to allow them to be delivered. And even if they are delivered, they won’t allow the scripts to function, so just avoid them altogether.

Instead of embedding these files into your email, try this workaround instead: Use a still image/screenshot of the video with a play button in the center that links to the video on your website or YouTube.

10. Move on.

Just like you should clean your email lists of unengaged users, you also need to check for ones whose contact information may have changed. People move countries, change jobs, or close out their email accounts. So, if you haven’t contacted them in a year or more, you should check whether they are still using the address before sending them an email marketing campaign.

Why is this important? Because older email addresses are more likely to have hard bounces, which could be a spam trap.

11. Email ASAP.

Did someone leave an item in their online cart? Send them a cart abandonment email ASAP. Did they just sign up for your newsletter? Send them a welcome email ASAP. Did they view a product without adding it to their cart? Send them a browse abandonment email ASAP. Did they make a purchase, and you need to send them a confirmation? Well, you get the point.

The quicker you email someone, the more likely they are to know who your brand is and why they are receiving your message. That’s important because if they don’t recognize your brand, they might mark it as spam or leave it unopened — which both negatively impact your rates.

12. Optimize your emails for mobile.

The number of people who view email on their phones is only going to go up from here (and it’s already a high percentage). So, your email campaigns better be optimized for these devices. 

Beyond simply showing up correctly on smartphones and tablets, you also need to consider how the different components will appear. For example, there will be limited space for subject lines on a smartphone, so keep them short and sweet. And no one wants to scroll forever to read a long email on a phone. Not only is a short message easier for your recipients to look at, but really long emails can also trigger spam filters. So, test all of your campaigns on a mobile device before sending to be safe.

13. Know your brand.

From the tone of your subject line to the look and feel of your email body, you should make it all true to your brand. Use your brand’s fonts, colors, logos, and images from other marketing campaigns to make it clear who is emailing them. Brand recognition is a huge factor in keeping your message out of the spam folder, and it also helps build trust with your audience.

14. Read everything. And then read it again.

What’s your first thought when you read an email that has a typo or poor grammar? It’s not very professional, right? That’s why it’s so important to proofread every campaign before you hit send. If editing isn’t your forte, send a test email to a coworker to have them read it. 

Having a misspelling doesn’t only appear unprofessional, but it is also a spam trigger. So, make sure your email is clean before it goes out. You can always use free services like Grammarly to help catch major errors.

15. Steady wins the race.

Something else that can set off the spam alarm is sending uneven batches of emails. For example, if you have 20,000 contacts on your email list, don’t send emails out to 60 percent the first time, 5 percent the second, and then 35 percent at the end. You want to try to keep the numbers steady throughout the sending process.

16. Avoid spam words (duh).

This might sound obvious, and it is — if you know which words are considered spammy. Your ESP is likely to flag any major spam words, but it’s good to have a sense for what is considered spammy. Things about winning, money, or enhancements are big red flags. Here are a few of those spam keywords to avoid:

  • 100% free
  • Apply now
  • Billing
  • Bargain
  • Call
  • Deal
  • Hidden
  • Medicine
  • No obligation
  • Stop
  • This isn’t spam

Oh, the irony on that last one. Try to keep your text conversational and not gimmicky, and you’re off to a great start.

17. Write truthful subject lines.

You might feel pressured to come up with a clever, catchy subject line. It’s what makes people open your email, right? True, but the subject line’s main purpose is to tell the recipient what they will find if they open the email. 

It needs to convey an accurate message — not simply something to catch their attention. You need to be able to produce the goods for whatever the subject line promises them. So while a mysterious or interesting subject line might sound great, it might not properly convey what’s in the message.

18. Provide targeted content.

A great way to do that is by segmenting your lists and only sending contacts what you know they’ll be interested in receiving. You wouldn’t send an email about pet supplies to someone who signed up for your newsletter on gardening supplies. 

The content needs to be relevant for them. Not only will that help reduce your number of unsubscribes (which hurts your metrics), but that also personalizes your messages and better engages your audience. Generic emails tend to be marked as unwanted emails.

19. Balance text and images

Did you know spam filters can’t read images (at least not at the moment)? So, you need to make sure you have a good mix of text and visual elements. While you might want to send the entire email as an image design so it appears exactly like you planned, the spam filters won’t know what it’s about and if it’s good or bad.

(Hint: You want to make it as clear as possible that your email is one of the good ones.)

20. Email your lists regularly.

Don’t be a stranger when it comes to your subscribers. Just like you get to know new friends by talking with them regularly, the same is true for your email audience. So, if you rarely email them and suddenly start sending them frequent messages, that can be a red flag for spam filters. The same is true if you stop sending them emails abruptly and then start back again in a few months. ISPs won’t be too happy about that.

You want your campaigns to be consistent — whether that’s daily, weekly, or monthly. Find the rhythm that works best for your brand and audience, and stay true to it.

21. Let them know who it’s from.

Whether it’s the brand name or the name of a prominent person in the company (ex. CEO, marketer who always sends out emails, etc.), make sure your emails are coming from a name the recipient will recognize. They tend to mark an email as spam if they don’t know who it’s from.

22. Survey your subscribers.

We’ve talked a lot about providing your email subscribers with content they will enjoy and find valuable. But, how do you know if you are achieving that goal? Simple: Ask them.

Beyond looking at metrics to see which campaigns performed the best, you can also survey your subscribers to get a better idea of what they want to receive and if they like what you’re sending. You can ask them for feedback on things like the type of content they receive, email frequency, and what you can improve on. Then, put those findings into action.

23. Perform A/B tests.

Do your subscribers prefer campaigns about upcoming sales, or would they rather see your latest blog posts? Try sending both and see which one performs the best. Just be sure to only test one variable (ex. subject line, image, CTA) at a time when performing A/B tests so you can get accurate results.

24. Have a conversation.

All of your marketing campaigns should sound natural, like you’re having a conversation with a friend. Don’t use industry terms or verbiage that could cause a reader to stumble or become confused. Not only will you confuse the recipient, but you could also confuse a spam filter, and you know what that means (i.e. not good).

Try reading your content out loud to see how it sounds. If you wouldn’t say it to a friend, don’t write it in an email.

25. Ask contacts to whitelist your email address.

This is the golden ticket to keeping your messages out of spam. Sure, not every contact is going to want to take the time to do this, but it can’t hurt to ask if they will. If they value the content you send, they aren’t going to want to miss any of your messages — making them more likely to add your email address to their address book. And that’s something spam filters really respect.

26. Don’t include large image files.

Sending an email with a large image is a good way to trigger the spam filter. There’s an easy fix for that, though. Use the web-resolution version of an image to prevent that issue, while still sending them some visually appealing campaigns.

27. Know your email metrics.

To figure out if something is off (and possibly harming our reputation), you need to be tracking your email metrics. And here are the metrics to be looking at:

28. Test different providers.

We mentioned how important it is to optimize your emails for mobile to ensure they are appearing the way you intended. But, it’s also important to make sure your messages are displaying correctly with each email provider.

For example, your email might look great for a Gmail user but then not so great for someone using Outlook. So, make sure you test with different providers.

29. Don’t embed forms.

Most email providers don’t support forms that are directly embedded into the email message because of possible security risks. Instead, include a clear CTA that links to a landing page with the form.

30. Use a reputable ESP.

You work hard to build your reputation, so only use an ESP that does the same. Look for ones that have established track records with a variety of ISPs, which will mean their servers have good reputations. That will help give your emails a better chance of being delivered.

Plus, if one of your emails happens to hit a spam trap and puts you on a blacklist, the ESP can help sort out the issue on both sides.

31. Stay away from red fonts.

There are plenty of other colors to choose from, so just don’t use red as your font color. Red can be associated with being negative, so there’s really no reason for it. Also, don’t use white text on a white background because this is a common practice of spammers and will cause your email to get flagged.

32. Don’t go SEO crazy.

Google doesn’t like sites that throw massive amounts of keywords into their posts in an attempt to improve its rankings. And the same can be said for emails and spam filters. Stuffing emails with keywords is harmful for the consumer experience because who wants to read something like that? And if they don’t want to read your email, you know where it’s going to end up.

Again, this issue can be fixed by writing like you would talk. You are writing to other people, you know?

33. Let people unsubscribe.

Not only is this part of the CAN-SPAM Act, but giving your audience a way to unsubscribe will reduce spam complaints. Simply include an “Unsubscribe” link in your template that takes them to a page where they can either unsubscribe from all of your communications or specific lists.

When they unsubscribe, you’re required by law to remove them from your lists. If you choose to do this manually, make this a top priority. 

Include the Unsubscribe option at the top or bottom of your email.

34. Include their name.

Just like you should include a sender’s name, you should also make sure to include your recipient’s name in the “To:” field. That shows them (and spam filters) that you know your recipient.

35. Make the email viewable in web browsers.

Of course, you want your email to appear perfectly in their inbox. However, no matter how hard you try, an email client can still display the email poorly. So, make sure to include a link that will allow them to view the entire message in a web browser.

36. Use alt text in images.

Several email clients block images by default. And if that’s the case, your recipients won’t see any of your images unless they click a button to show them — or if they change their default settings. By adding alt text to the images in your emails, they’ll be able to understand your message even if they can’t see the images.

That’s especially important to do if you use an image as your CTA. With the alt text, they wouldn’t see anything. However, when you add the alt text to the image, they will know where to click to follow the CTA.

37. Authenticate your domain and emails.

To keep malicious users from mimicking your domain to scam your subscribers, you’ll want to authenticate your domain and emails. By doing that, you’ll signal to ISPs that your emails are really being sent from your domain and can be safely delivered to your subscribers’ inboxes. Here are four ways you can do that: DKIM, SPF, Sender ID, and DMARC.

38. Choose the best send times.

One component of having a successful email marketing campaign is sending it at the right time. If it’s not hitting subscribers when they are most likely to read an email, they might not open it, which affects your metrics and sender score. So, check out when subscribers are opening emails, and perform A/B tests to see when you’ll get the best results.

Good email marketing = avoiding spam filter

With spam accounting for about 14.5 billion messages globally a day, it’s obviously a big problem for both email clients and consumers.

By following good email marketing best practices and compliance laws, you can keep your emails out of your subscribers’ spam folders and avoid becoming part of that statistic.

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