How to Avoid Email Spam Filters (and How They Work) | Clickback

How to Avoid Email Spam Filters (and How They Work) | Clickback

A major concern for email marketers is how to avoid email spam filters.

We’ve covered the difference between cold email and spam time and again on this blog but the fact of the matter is, even if you have a perfectly legitimate offering that’s both relevant and useful to your targeted email list, there are still factors at play that could trigger spam filters into mistakenly thinking you belong in the junk folder.

For your email campaigns to be effective, you need to make sure that people actually see them, and the chances of that happening from the junk folder are slim. But with spam filters changing and evolving all the time, how can you stay ahead of them?

The key is to evolve with the spam filters and ensure that nothing you’re including in your email campaigns is going to give them the ammunition they need to relegate you to the dreaded spam box.

We’d all love to just write our email and get on with our day, but a little bit of extra work can go a long way towards ensuring your campaigns have as many eyes on them as possible. It can be a bit of a chore to keep up with spam filters, but at the end of the day, it’s worth it to familiarize yourself with the practices that will help improve your overall deliverability.

How to Avoid Email Spam Filters

What is a Spam Filter?

Before we can talk about how to avoid email spam filters, it’s important to know how a spam filter works. A good way to visualize a spam filter is to think of…well…a filter. It’s a virtual access control system that reviews incoming email and prevents anything that might be considered ‘spammy’ from reaching the inbox.

Spam filters analyze various data points in the email to determine whether or not it’s spam. Mailbox providers (like Google and Microsoft) also utilize what’s known as a spam score based on that criteria to determine if an email can pass through the filter.

In a nutshell, a spam score is a number between 1 and 100 that determines how spammy your email is. The higher the number, the more likely your email is spam and the less likely you are to reach the inbox.

While there are a large number of data points spam filters use to identify spam, the main ones are:

  • Sender identity
  • IP and domain reputation of the sender
  • Subscriber behavior
  • Email content

There…once you break the spam filter’s behavior down into four main components, it doesn’t seem so scary, does it?

You can drastically improve your deliverability and avoid email spam filters by keeping the following best practices in mind.

Sender Identity

Spam filters will analyze your IP addresses and domains to create a sender identity which tracks historical data and sending behaviors that can impact how you’re able to send email in the future.

Therefore, if your IPs and domains have been used to send spam in the past, it will become more difficult to send future emails. Spam filters generally use one to three forms of identify authentication to build sender identities.

  • Sender Policy Framework (SPF) records identify which email servers are allowed to send on behalf of the domain. These records prevent spammers from sending messages with falsified ‘from’ addresses.
  • DomainKeys Identified Mail (DKIM) records let organizations take responsibility for a message that’s sent. The organization’s reputation is the basis for evaluating whether to trust the message in the future.
  • Domain-Based Message Authentication, Reporting & Conformance (DMARC) records leverage the SPF and DKIM authentication protocols to help communicate to mailbox providers how to treat email with a forged sending domain.


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IP and Domain Reputation

Your sender reputation can have an impact on your deliverability as well. If your IPs and domains have a low reputation score, then they aren’t likely to be let past a spam filter that’s meant to weed out email from lower-quality senders.

Some of the factors that can affect your IP and domain reputation are:

  • Complaints lodged against email coming from your address
  • Volume of email sent from your domains/IPs
  • The type of email addresses you’re sending to – spam traps/bad data etc.
  • If you’ve been blacklisted

For these reasons, it’s not recommended that you send cold email from your own domain. The last thing you want is to get your address blacklisted because you sent too many emails to too many harmful addresses, preventing you from further email marketing.

Key Takeaway: In order to keep your sender identity and reputation in check, it’s important to find a platform that sends your campaigns using IPs and domains that are going to keep you safe.

It’s also important to note that the quality of your email list plays a major role in your deliverability, and running it through an email verifier to remove any spam traps, bad data, old email addresses, and honeypots can drastically improve the performance of your campaign.

Subscriber Behavior

Another area that determines whether a spam trap will let you through to the inbox is how your recipients tend to engage with your content once they’ve received it. Spam filters use all kinds of interactions with your email to detect how you should be classified.

If people are complaining about your email, moving it right to the junk folder or marking it as spam, this indicates to a spam filter that your emails are not interesting to your recipients. The same is true if a large number of people delete your email without opening it.

Have you ever ventured into your junk folder and found that a newsletter you purposely subscribed to was automatically winding up there? Chances are, you were deleting these messages sight unseen and your mailbox provider’s spam filter decided that the emails must be spam.

Conversely, if someone goes into their junk folder and moves your message back to the inbox, this tells the spam filter that your email is not junk and will likely lower your spam score.

Your spam score is also less likely to go up the more reads your email has. If a spam filter determines that people are opening and reading your email – a metric typically measured on a time-based system –  your spam score is likely to improve because of it.

Key Takeaway: Your recipients’ interactions matter! Your job as an email marketer doesn’t stop once you’ve hit send. Remember, you need to make sure that the email content you’re sending is relevant and useful to the people who are receiving it. Otherwise they’re likely to delete your email before they’ve even read it, and your spam score will suffer.

If you’re experiencing a high number of deletions and it seems like no one is reading your emails, address your buyer persona or revise your content. Make sure you’re sending something that’s going to benefit your recipient in some way.


The content of your email is important because, as an email marketer, it’s probably what you have most direct control over in terms of deliverability.

Even when your emails are targeted, your offerings are legitimate, and your content is useful to your recipients, you might still trigger a spam filter if you’re including words, phrases, or design choices that are commonly used in spam emails.

Using something like ‘FREE!!!!’ in all caps with (way) too many exclamation points in your subject line might seem like it’s going to stand out in an inbox, but this is a common tactic used by spammers, and it’s likely going to get you moved to the junk folder by a spam filter automatically.

Likewise, designing an email that consists of mostly (or only) images is another common spam tactic that’s picked up on right away by spam filters and no longer flies.

This is because, as I mentioned before, spam filters are constantly evolving. Once spammers caught onto the fact that filters were picking up on certain words they were using, they contained them in images and sent them off – now spam filters know to look out for image-heavy emails.

Key Takeaway: Spam filters are smart. Familiarize yourself with the ‘spammy’ practices that are likely to trigger spam filters and avoid using them. For best results, use a spam checker to make sure that you aren’t overlooking any problem areas with your campaign.

Make it Past the Ultimate Spam Filter

These are arguably the most important factors to consider when looking to avoid spam filters, but beyond this, you should be putting your best foot forward when it comes to designing your emails to pass the test of the most intelligent spam filter – your recipient.

See, even when your email makes it past the mailbox provider’s spam filter, if your recipient doesn’t deem your email worth his or her time, they’re going to do the filtering themselves.

Be sure to proof-read your email thoroughly. There’s nothing more noticeable in an email campaign than grammatical errors. Proof your email, then proof it again. If you have the resources, get someone else to look at your email to make sure there are no glaring errors. Egregious spelling and grammar mistakes are a telltale sign of spam and will stick out like a sore thumb to your recipients.

Similarly, make sure that there are no major discrepancies between your email’s preview info and body content. Subject lines should expressly correlate with the content of the email, and your name should match up with the ‘from’ email. Any inconsistencies in your email might be a red flag to your recipient and they’re likely to delete your email because of them.

Remember to include a physical address where you can be reached in your email as well. This is an email marketing requirement and messages that are missing this are more than likely spam.

One of the most efficient ways that you can ensure a high deliverability rate and avoid spam filters is to use the right tool for the job when sending your email marketing. Clickback MAIL was designed for cold email with deliverability in mind. It features a live spam checker that will provide you with your spam score before you send your campaigns to help identify and eliminate problem areas. This, in conjunction with its proprietary IPs and domains and built-in email verifier mean that you can be confident that your emails will land in the inbox.

You likely already know that your emails aren’t spam, but the spam filters might need a little extra convincing. Hopefully this has given you some insight into how you can bypass them in your next email campaign.

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