Do specific email keywords trigger spam filters and influence unsubscribe rates?
Michael Ko
Co-founder & CEO, Suped
Published 13 Jun 2025
Updated 19 Aug 2025
7 min read
The question of whether specific keywords in an email trigger spam filters and influence unsubscribe rates is complex. For years, email marketers have been advised to steer clear of certain words, fearing their messages would instantly land in the dreaded spam folder. While there's a grain of truth to this, the landscape of email deliverability has evolved considerably.
Modern spam filters, powered by sophisticated artificial intelligence and machine learning, analyze far more than just individual words. They look at the overall context, sender reputation, engagement metrics, and various technical authentications (like SPF, DKIM, and DMARC) to determine an email's legitimacy. This means a single word, even one historically flagged as spammy, is unlikely to be the sole reason an email goes to spam.
Unsubscribe rates, on the other hand, are almost entirely driven by recipient behavior. While an email landing in the spam folder might prevent an unsubscribe from happening (because the recipient never sees it), keywords themselves rarely directly cause unsubscribes. Instead, they might contribute to a negative perception of your email, which then leads to an unsubscribe.
The evolving role of keywords
Years ago, lists of spam trigger words were highly influential. Terms like free,guarantee, or urgent were almost certainly going to land your email in the junk folder. This led to marketers meticulously auditing their copy to avoid these terms at all costs. While it's still good practice to be mindful of overly promotional or misleading language, the direct impact of specific keywords alone has diminished significantly. Many email providers have confirmed that focusing solely on a spam word list is an outdated approach.
Today, mail servers (receiving domains) employ far more sophisticated methods. They analyze patterns, sender history, recipient engagement, and even the combination of different elements within an email, not just isolated keywords. An email with excellent sender reputation that uses a word like free in a natural, non-misleading context is very unlikely to be blocked or blacklisted solely for that reason. Conversely, an email from a poor reputation sender that avoids spam words could still go to spam due to other factors.
This shift means that instead of obsessing over specific terms, the focus should be on overall email content quality, relevance to the recipient, and maintaining strong sender metrics. It’s about building trust, not just avoiding red flags.
Old approach
Rigid adherence to lists of spam trigger words, avoiding them regardless of context.
Belief that a single bad keyword could instantly send an email to spam.
Understanding that spam filters evaluate context, sender reputation, and recipient engagement patterns.
The true drivers of spam filtering
Spam filters don't just scan for a list of forbidden words. They assign a spam score to each incoming email based on hundreds of factors. While certain phrases might contribute a small fraction to this score, the heavy lifting is done by much broader indicators. The overall message content, including the ratio of text to images, image quality, and link structure, also plays a part. Poorly constructed emails, excessive links, or suspicious formatting can raise red flags more effectively than a few spammy words alone.
The most significant factor influencing whether your email lands in the inbox or the spam folder is your sender reputation. This is a measure of trust that internet service providers (ISPs) and email service providers (ESPs) like Gmail and Outlook assign to your sending domain and IP address. A strong reputation, built on consistent sending of valuable, engaged content, will almost always override minor keyword concerns.
Factors that damage sender reputation, such as high bounce rates, spam complaints, and sending to unengaged lists, are far more detrimental than any single keyword. Ensuring proper email authentication and a clean email list are paramount for good deliverability.
Focus on reputation, not just keywords
While it's wise to avoid blatantly deceptive or aggressive language, a well-maintained sender reputation and engaged audience will largely mitigate the impact of specific keywords (or 'spam words'). Spam filters weigh numerous signals, with reputation being among the heaviest. Prioritize good sending practices over an exhaustive blacklist check on words alone. You can learn more about how email blocklists work.
Unsubscribe rates: a matter of recipient choice
Unsubscribe rates are primarily a reflection of recipient satisfaction and the relevance of your email content. An email that is irrelevant, too frequent, or simply no longer desired by the recipient is far more likely to trigger an unsubscribe than one containing a specific keyword. If your content consistently provides value, you'll see lower unsubscribe rates, regardless of the occasional sales or offer related terms.
There's an indirect connection, however. If your emails consistently land in the spam or junk folder due to poor sender reputation or other issues, your recipients won't see them. This means they can't unsubscribe. While this might seem like a good thing for your unsubscribe rate, it's actually disastrous for deliverability and engagement, ultimately harming your sender reputation and campaign effectiveness.
Conversely, a high unsubscribe rate can signal to ISPs that your content isn't relevant to your audience, negatively impacting your sender reputation. It's a delicate balance, but one where recipient perception of value outweighs minor content considerations like specific keywords.
Factor
Impact on unsubscribe rate
Relevance
Sending content that doesn't meet recipient expectations or interests leads to higher unsubscribes.
Frequency
Too many emails can overwhelm recipients, prompting them to unsubscribe.
List acquisition
Poor quality or purchased lists often result in high unsubscribe rates and spam complaints.
Content quality
Emails that are poorly written, hard to read, or contain broken links (or commented code) can lead to frustration and unsubscribes.
Email design
Unresponsive design or an email template that renders poorly can prompt recipients to opt-out.
Holistic deliverability strategies
To ensure your emails reliably reach the inbox and maintain low unsubscribe rates, it's essential to adopt a holistic approach to email deliverability. This means looking beyond individual keywords and focusing on the bigger picture of your email program.
Prioritize building and maintaining a strong sender reputation. This involves sending consistent volumes, avoiding spam traps, and ensuring high engagement rates. Regularly clean your email lists to remove inactive or invalid addresses, and always send to an opted-in audience. Implementing proper email authentication protocols (SPF, DKIM, and DMARC) is also crucial, as it verifies your identity as a legitimate sender and prevents impersonation.
Beyond technical aspects, focus on crafting valuable, relevant, and engaging content. Personalize your messages where possible, segment your audience, and respect their preferences regarding sending frequency and content types. A clear and easily accessible unsubscribe link is a must, as it provides a graceful exit for disengaged subscribers, preventing them from marking your emails as spam, which is far more damaging to your reputation.
Views from the trenches
Best practices
Continuously monitor your sender reputation across major ISPs to identify and address issues proactively.
Segment your audience based on engagement and interests to send more relevant and targeted emails.
Implement a double opt-in process for new subscribers to ensure a truly engaged and verified list.
Regularly clean your email list by removing inactive subscribers, hard bounces, and known spam traps.
Common pitfalls
Over-reliance on outdated spam keyword lists, ignoring more critical deliverability factors.
Sending emails to purchased or old lists, leading to high bounce rates and spam complaints.
Failing to monitor and analyze email engagement metrics, missing signs of disinterest.
Not having easily visible and functional unsubscribe links, forcing users to mark emails as spam.
Expert tips
Prioritize building trust with your audience through consistent, valuable content and respecting their inbox.
Focus on sender authentication (SPF, DKIM, DMARC) to prove legitimate identity and prevent spoofing.
Understand that inbox placement is dynamic; continuous monitoring and adaptation are key.
Ensure your email content is well-structured, mobile-friendly, and provides a clear call to action.
Marketer view
A marketer from Email Geeks says that sender reputation always outweighs the impact of specific keywords.
2023-10-26 - Email Geeks
Marketer view
A marketer from Email Geeks explains that unsubscribes are typically recipient-driven actions, influenced by subject lines, pre-headers, user expectations, and email content, not direct spam filter triggers.
2023-11-01 - Email Geeks
The path to better email engagement
In conclusion, while it's beneficial to write clear, concise, and non-deceptive email copy, the idea that specific keywords alone will trigger spam filters and ruin your unsubscribe rates is largely a myth in today's email environment. Modern spam filtering is far more sophisticated, focusing on a multitude of signals, with sender reputation being paramount.
Unsubscribe rates are almost exclusively driven by recipient engagement and satisfaction. By focusing on building a strong sender reputation, maintaining a clean list, and providing consistent value, you can significantly improve your email deliverability and cultivate a happy, engaged subscriber base.
Shift your focus from micro-managing spam trigger words to developing a robust, recipient-centric email strategy. This approach will not only help you avoid spam folders but also foster better relationships with your audience, leading to long-term success.
Gmail and 
Outlook assign to your sending domain and IP address. A strong reputation, built on consistent sending of valuable, engaged content, will almost always override minor keyword concerns.
