Do specific email keywords trigger spam filters and influence unsubscribe rates?
Michael Ko
Co-founder & CEO, Suped
Published 13 Jun 2025
Updated 13 Oct 2025
7 min read
For years, email marketers have worried about specific keywords triggering spam filters and leading to poor deliverability. The fear of using words like 'free', 'guarantee', or even seemingly innocuous terms, often dictated content strategy. However, the world of email filtering has evolved significantly beyond simple keyword matching. Today, the factors determining whether your email lands in the inbox or the spam folder are much more nuanced.
While some phrases can still raise a flag, they are rarely the sole reason for an email being blocked or directed to spam. Modern spam filters use sophisticated algorithms that analyze a wide array of signals, including sender reputation, email authentication, recipient engagement, and the overall context of your message. This comprehensive approach means that isolated keywords have less impact than they once did, though they aren't entirely irrelevant.
Similarly, the relationship between email keywords and unsubscribe rates is often misunderstood. Many believe that certain words directly cause recipients to opt out, but it's usually a deeper issue related to relevance, audience expectations, or the overall communication strategy. Understanding these dynamics is crucial for maintaining a healthy email program and ensuring your messages reach their intended audience effectively.
The evolving role of spam trigger words
The concept of "spam trigger words" originated in an era when email filters were less sophisticated. These filters heavily relied on pattern matching, flagging emails that contained terms commonly associated with unsolicited bulk mail. Lists of these words became widespread, and marketers diligently tried to avoid them. However, as spammers adapted, so did the filters.
Today, an email with a few potentially spam trigger words is unlikely to be flagged if its other attributes are strong. Factors such as your sending domain's reputation, IP address reputation, and recipient engagement carry far more weight. For instance, an email about medical fraud from a reputable financial institution is less likely to hit a spam trap than a suspicious email offering a free prize from an unknown sender. The context of keywords matters a great deal.
This shift means that obsessing over specific spam words is often a misdirection of effort. While it's wise to avoid overly sensational or deceptive language, especially in subject lines, a comprehensive approach to email deliverability is far more effective. This involves ensuring proper email authentication, maintaining a clean sending list, and consistently providing valuable content to your subscribers.
Are spam trigger word lists still relevant?
Many HubSpot and ActiveCampaign articles still provide lists of spam trigger words, but their emphasis has shifted. The general consensus is that these words are now just one small signal among many. It's more about the overall pattern and sender behavior than individual words. A good sender reputation can often override the negative impact of a few problematic terms.
Beyond keywords: The true drivers of inbox placement
If keywords aren't the primary culprit, what is? The answer lies in sender reputation and robust email authentication. Internet Service Providers (ISPs) like Gmail and Yahoo meticulously track a sender's history, looking at metrics like spam complaint rates, bounce rates, and engagement levels. A strong sender reputation signals to ISPs that you are a legitimate sender of desired mail.
Beyond reputation, proper email authentication is non-negotiable. Standards like SPF, DKIM, and DMARC prove that your emails are legitimately from your domain and haven't been tampered with. Without these, even perfectly crafted emails can land in spam, regardless of their content. Implementing DMARC with a tool like Suped DMARC monitoring helps you gain visibility into your email flows and quickly identify authentication failures that could impact your deliverability.
Engagement also plays a significant role. When recipients open, click, and reply to your emails, it sends positive signals to ISPs. Conversely, low engagement or a high number of deletions without opening can negatively affect your standing. This feedback loop is continuous, meaning your sending practices directly influence your future inbox placement. Regularly checking your blocklist status is also important, as being listed on a DNSBL (real-time blockhole list) can severely impact your reach.
Understanding unsubscribe rates: user perception vs. filters
Unsubscribe rates are almost exclusively driven by recipient actions, not direct spam filter triggers. When someone unsubscribes, it’s because they’ve seen your email (or at least the subject line) and decided it's no longer relevant or desired. This is a critical distinction, as it shifts the focus from avoiding trigger words to understanding and meeting your audience's expectations.
However, a sudden spike in unsubscribes, especially across specific domains or shortly after a send, can be perplexing. While usually a sign of recipient disinterest, there are edge cases where automated systems might play a role. Some email clients (or security systems) may pre-fetch or click all links within an email for security scanning. If your unsubscribe mechanism is a single-click process, these automated clicks could inadvertently trigger unsubscribes.
User-initiated unsubscribes
Recipient action: A deliberate choice by the subscriber after viewing the email content or subject line.
Content relevance: Often due to content not matching expectations or becoming irrelevant over time.
Engagement decline: A natural part of list decay, indicates a need for re-engagement or list hygiene.
Automated system unsubscribes
Security scanning: Some systems, especially at large organizations, click links to scan for malicious content.
Single-click unsubscribes: If a single click confirms unsubscription, security scans can cause unintended opt-outs.
Rate limiting: Some platforms employ a two-step unsubscribe process to prevent this issue.
To mitigate this, implement a two-step unsubscribe process where recipients confirm their decision. This ensures that actual human intent is behind each unsubscribe. It's also crucial to monitor your unsubscribe rates for unusual patterns and investigate anomalies, especially if they appear to come from specific domains. High unsubscribe rates, whether intentional or not, will negatively impact your sender reputation over time.
Monitoring your unsubscribe rates and deliverability closely is essential. Tools like Google Postmaster Tools can provide valuable insights into your domain's reputation and spam rate, helping you identify and address issues proactively. A clear trend of rising unsubscribes indicates a need to re-evaluate your content, frequency, or targeting.
Best practices for improving deliverability and engagement
Improving your email program involves a holistic approach that prioritizes sender reputation, authentication, and recipient experience over simply avoiding a list of words. Focus on building a trustworthy sender identity that ISPs will favor. This includes setting up and maintaining proper email authentication records like SPF, DKIM, and DMARC.
Regularly clean your email list to remove inactive or invalid addresses, which can inflate bounce rates and signal poor list management. Segment your audience to ensure that the content you send is highly relevant to each group, increasing engagement and reducing the likelihood of unsubscribes. Always deliver on the promise of your subject line, avoiding deceptive tactics that could lead to spam complaints.
Finally, monitor your email performance diligently. Utilize tools like Suped for comprehensive DMARC reporting and monitoring to gain deep insights into your email deliverability, authentication rates, and potential issues. This proactive approach allows you to quickly identify and resolve problems, ensuring your emails consistently reach the inbox and drive meaningful engagement.
Views from the trenches
Best practices
Always prioritize sender reputation over individual keywords for email deliverability.
Implement a two-step unsubscribe process to prevent accidental opt-outs by automated systems.
Regularly audit your email list for inactive subscribers to improve engagement metrics.
Utilize DMARC reporting tools to monitor email authentication and identify issues.
Segment your audience and personalize content to maintain high relevance.
Common pitfalls
Relying solely on old 'spam trigger word' lists without understanding modern filtering.
Having a single-click unsubscribe process that can be triggered by automated scanners.
Neglecting email authentication standards like SPF, DKIM, and DMARC.
Ignoring sudden spikes in unsubscribe rates or low engagement metrics.
Sending inconsistent content that doesn't align with subscriber expectations.
Expert tips
Monitor your own email sending and unsubscribe process as if you were a recipient.
Contextual relevance of keywords is more important than the words themselves.
Automated system clicks on unsubscribe links are less common with two-step processes.
A strong IP and sender score don't guarantee inbox placement if content is poor.
Consider overall email structure and list hygiene for optimal deliverability.
Marketer view
Marketer from Email Geeks says reputation consistently outweighs the impact of specific keywords in email deliverability.
September 20, 2019 - Email Geeks
Marketer view
Marketer from Email Geeks says unsubscribes are typically recipient-driven actions, influenced by factors such as subject lines, pre-headers, user expectations, and overall copywriting, rather than direct spam filter actions.
September 20, 2019 - Email Geeks
Prioritizing trust and relevance for email success
In summary, while specific keywords can still play a minor role, their impact on spam filters has significantly diminished. Modern email deliverability is primarily governed by a strong sender reputation, proper email authentication (SPF, DKIM, DMARC), and consistent recipient engagement. Unsubscribe rates are almost always a reflection of recipient sentiment and content relevance, not direct actions by spam filters.
By shifting focus from keyword avoidance to building trust and delivering value, you can dramatically improve your inbox placement and foster a more engaged subscriber base. Proactive monitoring and continuous optimization of your email program are key to navigating the complexities of email security and deliverability effectively.
Many HubSpot
and ActiveCampaign articles still provide lists of spam trigger words, but their emphasis has shifted. The general consensus is that these words are now just one small signal among many. It's more about the overall pattern and sender behavior than individual words. A good sender reputation can often override the negative impact of a few problematic terms.
