How to Beat the Spam Filters?

Feb 11, 2022

These days, email service providers are on a more intense mission than ever before to eliminate spam from their users’ inboxes.

Whenever you send a marketing email, you can be guaranteed that it is going to go through a spam filter before it gets to its next destination.

Ideally, you want it to pass and land in your recipient’s inbox, but if you’re using too many spam trigger words in the subject line or the email appears to be spammy, your message could end up in the spam folder even if it is legitimate.

So, here is how to take your email marketing services to the next level and land in primary inboxes, every time.

What are email spam filters?

Internet service providers and email providers use spam filters to detect any emails that are unsolicited or unwanted. Once the spam filter has identified a message that is likely to be spam, the message will be blocked from reaching the target user’s email address.

spam filters


Spam filters are a response by the industry to the increasing spam rate perpetrated by online fraudsters, and a measure taken to keep email users safe. 

Based on your likelihood to send unwanted emails, each sender gets their own spam score. The lower the score, the better position you are in and the less likely you are to end up in the junk folder.

No matter the email volume you send out, getting familiar with spam filters is a smart way to future-proof your campaigns and ensure better email deliverability.

How do email spam filters work?

Spam filters go through email messages using a set of rules and algorithms to look for and filter out emails that have spammy traits. The algorithm will then calculate the probability of the message being spam before assigning a value to each part of the message.

If the total value is more than the threshold, the message will be flagged as spam by the email tool and be sent to the spam folder. Email and internet service providers use different spam filter forms; each of these uses different criteria and rules to determine whether or not a message is spam.

Email spam filters were invented for a number of reasons. Primarily, it helps email recipients get only the emails they want. For email senders, these filters help comply with anti-spam laws such as the CAN-SPAM Act in the United States and GDPR in Europe.

Abiding by these rules can help you improve your inbox placement rate and it keeps recipients from receiving malicious emails. So, both you and your contact list win and the world is filled less junk email.

Header filters

These check email headers for any suspicious information. For example, they might check for fake email addresses. The filter will also go through the sender and recipient information along with the subject field, checking for spammy traits such as misspelled words.

The header contains the reply email, so pay special attention to format it properly if you want to land in inboxes, rather than the spam folder.

Content filters

These filters work by going through the content of an email to find spam trigger words. These are words and phrases that have cropped up a lot in spammy messages over the years such as ‘act now!’, or ‘no commitment needed’.

If you use these words a lot when sending to your email lists, some spam complaints are guaranteed to show up.

Blacklist filters

These filters check the IP address or domain name to check whether it is on a blacklist, to prevent blacklisted IP addresses or domain names from sending email messages to email clients.

The great news is that if you send legitimate emails, you can have yourself removed from a blacklist. If you send a large volume of emails, you could end up on a blacklist and hurt your sender reputation – but that can be fixed fairly easily.

Rule-based filters

This filter uses user-defined criteria to detect any spam. It goes through emails to look for words and phrases that appear spammy, assigning higher points to spam trigger words before calculating the final score. If it scores higher than a certain number, the email will be considered spam.

Permission filters

These filters will only allow through messages that the user has subscribed to and given permission to receive, preventing any unsolicited messages from reaching the inbox. To reduce spam complaints because of this filter, ask your recipients to add you to their address book.

Challenge-response filters

The filters go through the IP address of the sender to try and determine whether or not subscribers allow this sender to send messages to them.

How spam trigger words work

Some internet service providers and email providers will flag emails that have specific or suspicious content and words. Spam trigger words such as ‘money-back guarantee’ or ‘act fast’ may lead to your email being flagged and eventually, hurting a strong sender reputation.

spam trigger words


Spam trigger words are any words that have become associated with spammers over time, and it might be easier than you think for you to include these words in your message without even realizing it since spammers often use words like ‘free’ or ‘buy now’.

Spam trigger words to avoid in emails

Despite sometimes being used in a legitimate way, spam trigger words are any words that email service providers flag as suspicious and/or malicious. Using these words in your email body or subject can significantly hurt your email deliverability.

When too many of these spam trigger words are caught by the spam filter, the message will be routed away from the user’s inbox, going instead into the spam folder where it is unlikely to be received or opened. This is how your subscriber engagement tanks.

Carefully choosing the words that you include in email subject lines is the best way to avoid getting caught in spam filters and hurting your IP reputation. Your mailing list won’t even have to hit the spam button – your emails will be flagged as spam messages by default.

Should you use a spam trigger words checker?

It’s worth bearing in mind that spam trigger words alone are not always enough to send emails straight to spam with your subscriber list.

Email service providers know that it’s not just spammers that are sending emails offering discounts and sales; legitimate senders will also want to send emails to their subscribers advertising these offers that the user might be genuinely interested in learning about.

Because of this, it is important to understand all the different factors that are involved in identifying an email as spam and use a spam trigger words checker to get a better idea of how likely your email is going to be flagged by spam filters based on its content and subject line.

Most email marketing software does not have a list of words that you should not use to protect your email sender reputation. That’s why being familiar with these words is crucial for legitimate email sending and bypassing email filters.

Common spam words to avoid

When writing email content and subject lines, there are a few things that you can do to avoid your emails appearing spammy. You should avoid over-promising or over-sensationalizing your content or products, and don’t use any weird and wonderful formatting that might make you stand out in the inbox.

Spammers will often use tons of emojis and symbols in the subject line, and while this might work for grabbing attention, it can backfire on you if the email never makes it to the inbox as it is caught by the spam filter.

Some common words that might get flagged as spam trigger words include ‘buy’, ‘order’, ‘clearance’, ‘additional income’, ‘earn $’, ‘be your own boss’, ‘make money’, ‘extra income’, ‘affordable’, ‘bargain’, ‘cash’ ‘big bucks’, ‘cheap’, ‘cost’, ‘credit’, ‘fast cash’, ‘incredible deal’, ‘money back’, ‘price’, ‘one hundred percent free’, ‘no fees’, ‘no cost’, ‘no credit check’, ‘no hidden costs’, and many more.

While these sound like something you would include in promotional emails, the better choice is to use alternative expressions that are less likely to hurt your IP reputation and deliverability rate.

Of course, lots of the spam trigger words might be words and phrases that you are using legitimately. It’s important to consider both the email message as a whole and your reputation as a sender when determining how much of an impact these words are going to have in terms of getting caught in the spam filter.

Most of the time, however, you should avoid using them wherever possible and come up with more creative and original alternatives for commercial emails. Especially if you want cold email to succeed, you not only need relevant content but also originality to some extent.

How using email spam trigger words can harm your campaigns

Using email spam trigger words might not just send your emails to spam boxes instead of inboxes, but over time it can actually harm your email campaign.

Email service providers will notice if you are sending a lot of emails that are ending up in spam folders and might greylist your email address to check if you are a legitimate sender or even worse, assume that you are a spammer and blacklist your IP address, making it impossible for you to send further marketing messages.

Along with this, email providers are not the only ones looking out for spam trigger words.

Most email users have received their fair share of spam over the years and are quite familiar with the words and phrases that are frequently chosen by spammers.

This can lead to an increase in recipients ignoring your emails or even worse, mistaking them for spam and marking them as such, which will leave any further messages you send being sent to their spam box automatically.

Over time, this can harm your sender score and reputation, which will make it more difficult for you to send marketing emails that actually reach the right people. If you send bulk emails, this can make it very hard to succeed on any email platform.

Words and symbols you may not have realized were on the spam words list

While some spam words and symbols might be quite obvious, such as ‘win big’ or ‘huge deal’ accompanied by random symbols and excessive overuse of exclamation marks, others might surprise you. Adding a greeting such as ‘hello’, or ‘dear [name]’ can be seen as spammy, so it’s worth avoiding.

Calls to action in your email subject line like ‘click’ or ‘click here’ can also be a spam trigger worth steering clear of.

What to avoid as an email marketer

Avoid mentioning email marketing or direct marketing in your subject line and don’t mention things like sales, opting in, memberships, or 100% guarantees or satisfaction in your email body, especially if it’s cold emails coming from unfamiliar senders.

Depending on what you are marketing, there might be industry-specific spam trigger words to avoid, too. For example, if your emails are medical-related, avoid words and phrases like ‘medicine’, ‘weight loss’, ‘diagnostic’, or cures for things like aging, snoring, baldness, and more.

Finally, it should go without saying that mentioning spam in your email subject line is going to get the spam filter’s radar on high alert and you’ll go straight to the junk folder. You’re literally telling them that you are sending spam emails.

Sometimes spammers think that putting ‘this isn’t spam’ in the subject line will encourage recipients to read their email, but email service providers are on to that.

Spam filters use advanced algorithms to vet incoming emails and determine if they are legitimate or spammy using a range of different criteria. Understanding and avoiding spam trigger words is one of the simplest methods that you can use to avoid these incoming messages getting caught in spam filters.

Also, make sure to use double opt-in forms. These are signup forms where recipients have to confirm they are willing to receive emails from you before you put them on a list. This ensures more emails land in the inbox and over time, you’ll have fewer inactive contacts.

Sure, you’ll also have fewer individual subscribers, but you can keep your email list clean and have better email placement rates.

The best way to stay out of the spam folder

Want to improve your sender score, delivery rate and remove inactive subscribers? All it takes is validating your emails and your email reputation will be safe. Skyrocket your email deliverability by validating your entire list, and removing outdated, misspelled, and all types of invalid addresses.

You can do that with Bouncer today and get your first 100 validations completely free. Sign up now to get started and reach out to valid email subscribers only!

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