Do specific spam words still affect email deliverability?
Michael Ko
Co-founder & CEO, Suped
Published 13 Aug 2025
Updated 19 Aug 2025
6 min read
For years, email marketers and senders have been warned about so-called "spam words" and their potential to land emails in the dreaded junk folder. Lists of these words, ranging from "free" to "guarantee," became a staple of email marketing best practices. The prevailing wisdom was simple: avoid these words, and your emails would reach the inbox.
However, the landscape of email deliverability has evolved significantly. Modern spam filters are far more sophisticated than the keyword-matching algorithms of the past. The question now isn't simply whether a specific word is present, but rather how that word fits into the broader context of the email, the sender's reputation, and the recipient's engagement history. Let's delve into whether specific spam words still affect email deliverability.
The evolution of email spam filters
In the early days of email, spam filters were indeed quite rudimentary. They often relied on simple rule sets that flagged emails containing specific words or phrases that were commonly associated with unsolicited commercial email (UCE). If your email contained a high-scoring keyword like "Viagra" or "money fast," it would likely be diverted to the spam folder, regardless of your sender reputation.
This led to the proliferation of extensive "spam word lists" that marketers painstakingly avoided. While this approach offered some protection, it was easily circumvented by spammers who simply changed their phrasing, and it often penalised legitimate senders for innocent word choices. This simplistic approach also did not account for the complexities of language and context.
Today's email spam filters, particularly those used by major providers like Gmail and Outlook, employ advanced machine learning and artificial intelligence. They analyze thousands of data points to determine an email's legitimacy, moving far beyond simple keyword matching. This means a single spam trigger word alone is unlikely to send your email to the spam folder if your overall sending practices are sound.
What modern spam filters prioritize
Rather than focusing on isolated words, modern blocklists (or blacklists) and spam filters (or spam blocklists) prioritize a holistic view of email legitimacy. The most significant factor influencing whether your email reaches the inbox is your sender reputation. This reputation is built over time based on your sending volume, bounce rates, spam complaint rates, and engagement metrics.
Beyond reputation, strong email authentication protocols are critical. Implementing and correctly configuring SPF, DKIM, and DMARC tells recipient servers that your emails are legitimate and haven't been tampered with. Without these, even perfectly clean content can be flagged as suspicious. You can easily generate a DMARC record with our free tool.
Finally, recipient engagement plays a huge role. If your emails are consistently opened, clicked, and replied to, it signals to inbox providers that your content is valuable and desired. Conversely, high unsubscribe rates or, worse, direct spam complaints, will significantly damage your deliverability, regardless of whether you've used a single "spam word."
The multi-faceted nature of modern filtering
Today's spam filters evaluate email based on a complex interplay of factors, not just individual words. This includes sender reputation, email authentication (SPF, DKIM, DMARC), content patterns, sender IP history, recipient engagement metrics (opens, clicks, unsubscribes, spam complaints), and even the formatting and structure of your email. A single "spam word" won't ruin your deliverability if all other factors are positive, but a consistent pattern of problematic content combined with other issues will.
When content still matters
While isolated spam words have lost much of their individual power, content is by no means irrelevant. Filters now look for suspicious *patterns* within your email content that might indicate a spammy intent. This includes excessive capitalization, overuse of exclamation points, disproportionately large images compared to text, and hidden text. For instance, a high image-to-text ratio can be a red flag.
Additionally, some words or phrases, particularly those associated with specific regulated industries or illicit activities, will still carry more weight, especially if your sender reputation isn't pristine. For example, keywords related to pharmaceuticals or adult content are more likely to be flagged. Similarly, deceptive subject lines, such as starting a marketing email with "Re:" or "Fwd:" when it's not a reply or forward, can still trigger filters due to their misleading nature, as noted by Mailsoar. Learn more about email template changes that affect Microsoft deliverability in our guide.
It's not just about what words you use, but how they contribute to the overall message. An email with great sender reputation can get away with more. However, if your reputation is borderline, or if you're sending to unengaged lists, using overtly promotional language or deceptive tactics, even without traditional "spam words," can still tip the scales towards the spam folder. As Mailmodo explains, focusing solely on trigger words misses the bigger picture.
Old content triggers
Keyword-centric: Direct matches to a static list of "spam words" were heavily weighted.
Simple rules: Filters operated on straightforward if-then logic regarding specific terms.
Low context: Less consideration for the overall message or sender reputation.
Modern content relevance
Pattern recognition: Filters look for suspicious combinations of words, formatting, and overall message structure.
Contextual analysis: Content is evaluated in relation to sender reputation, authentication, and user engagement.
Deceptive practices: Misleading subject lines or content designed to trick recipients are still highly penalized.
Best practices for consistent inbox placement
To ensure your emails consistently reach the inbox, shift your focus from avoiding specific "spam words" to cultivating excellent email sending habits. This includes maintaining clean, engaged subscriber lists through explicit consent and regular list hygiene. Removing inactive or invalid addresses reduces bounces and improves your reputation.
Prioritize proper email authentication. Ensure your SPF, DKIM, and DMARC records are correctly configured and actively monitored. These technical foundations are far more influential on deliverability than any individual word in your content. Neglecting these can easily lead to your emails being flagged as spam, regardless of your content.
Finally, focus on creating valuable and engaging content for your audience. High open and click rates, coupled with low unsubscribe and spam complaint rates, are the strongest signals to mailbox providers that your emails are desired. Consistent positive engagement builds a robust sender reputation that can withstand minor content anomalies. This proactive approach will help you avoid the spam folder. Learn more about why your emails go to spam and how to fix it.
Factor
Impact on Deliverability
Action to Improve
Sender reputation
Crucial. Influenced by bounce rate, spam complaints, and engagement.
Continuously monitor your domain and IP reputation using tools like Google Postmaster Tools.
Implement a DMARC policy at 'quarantine' or 'reject' to protect your domain from spoofing.
Regularly clean your email lists to remove inactive subscribers and reduce bounce rates.
Common pitfalls
Relying solely on avoiding "spam words" and neglecting other critical deliverability factors.
Sending to unengaged lists, which leads to low open rates and high spam complaints.
Failing to set up or monitor proper email authentication protocols like SPF, DKIM, and DMARC.
Expert tips
Focus on the 'why' behind an email being flagged, rather than just the 'what' (individual words).
Understand that context, sender history, and engagement are paramount for modern filters.
Prioritize a strong sender reputation over an exhaustive list of words to avoid.
Marketer view
Marketer from Email Geeks says that while the term "spam words" sounds outdated, filters like SpamAssassin still assign points for certain content elements.
2019-12-09 - Email Geeks
Marketer view
Marketer from Email Geeks says that filters now subtract points for good sender scores and authentication, meaning positive factors are much more important than negative content triggers.
2019-12-09 - Email Geeks
Navigating email content in the modern era
The era of fearing specific "spam words" is largely behind us. Modern email deliverability is a nuanced field governed by sophisticated algorithms that assess an email's trustworthiness based on a myriad of factors. While problematic content patterns can still be an issue, individual words rarely doom an email on their own.
Instead, prioritize building a stellar sender reputation, ensuring robust email authentication, and consistently delivering valuable content that engages your audience. This comprehensive approach is what truly guarantees your emails land in the inbox, not just avoiding a list of arbitrary words.
Gmail and 
Outlook, employ advanced machine learning and artificial intelligence. They analyze thousands of data points to determine an email's legitimacy, moving far beyond simple keyword matching. This means a single spam trigger word alone is unlikely to send your email to the spam folder if your overall sending practices are sound.
