Does using the word 'Free' in email subject lines or content impact deliverability?
Matthew Whittaker
Co-founder & CTO, Suped
Published 21 May 2025
Updated 19 Aug 2025
6 min read
For years, the word 'free' was considered a red flag in email marketing, almost guaranteeing a trip to the spam folder. Marketers meticulously avoided it in subject lines and even within email content, fearing instant blacklisting (or blocklisting, if you prefer). This cautionary approach stemmed from an older era of spam filtering, where simple keyword matching played a much larger role in determining deliverability.
However, email deliverability is a dynamic field. Spam filters have evolved significantly, becoming far more sophisticated than mere word counters. They now employ complex algorithms, machine learning, and artificial intelligence to assess a multitude of factors when deciding whether an email reaches the inbox or gets flagged as spam. So, what's the truth about using 'free' today?
Context and sender reputation
Modern spam filters are designed to understand context, sender reputation, and recipient engagement rather than relying solely on a list of 'spam trigger words.' While a word like 'free' might still contribute to a cumulative spam score, it's rarely the sole factor determining an email's fate. The overall picture, including your domain's sending history, IP reputation, and subscriber interactions, carries far more weight.
The shift in filtering intelligence means that a single word, even one historically associated with spam, is unlikely to cause significant deliverability issues on its own. For example, a legitimate newsletter announcing a free webinar will likely land in the inbox if the sender has a strong reputation and good engagement metrics. Conversely, an email from a suspicious sender with poor authentication and low engagement, even without 'free' in the subject, is far more likely to be flagged.
Many marketers often wonder, do specific spam words still affect email deliverability? The answer lies in this evolving landscape, where a holistic view of email characteristics dictates delivery. It's less about avoiding a specific word and more about maintaining a healthy sending ecosystem.
Old approach
Historically, spam filters operated on simpler rulesets, often employing keyword matching as a primary defense. This led to a rigid list of 'spam words' that, if present, would significantly increase the likelihood of an email being blocked or sent to the junk folder. Marketers had to be vigilant in scrubbing their copy for these terms.
The focus was on the explicit content of the email, leading to a game of 'cat and mouse' where senders tried to bypass filters by using synonyms or obfuscating words. This approach, however, often resulted in legitimate emails being caught in the crossfire.
Today, it's about much more than just the words themselves. Consider the larger context of your email. Is it part of a legitimate campaign with proper email authentication (SPF, DKIM, DMARC)? Is your domain reputation strong? These factors are far more influential than the mere presence of a single word.
Sender reputation is built over time through consistent good sending practices, positive recipient engagement, and minimal spam complaints. If your sender reputation is solid, you have more leeway with your content, including words like 'free.' Conversely, a poor sender reputation can make even the most innocuous email content appear suspicious.
Mailbox providers like Gmail and Yahoo look at a holistic view. They consider factors such as your sending volume, bounce rates, spam complaint rates, and engagement rates (opens, clicks). A legitimate offer of something free, if it aligns with your audience's expectations and your sending history, is unlikely to be penalized.
The crucial role of engagement and complaints
Recipient engagement is a critical factor in deliverability. If your emails are consistently opened, clicked, and replied to, it signals to mailbox providers that your content is valuable and desired. This positive engagement can offset any minor flags from 'spammy' words. Conversely, low engagement or high complaint rates are far more damaging than any single word.
Spam complaints are perhaps the most direct negative signal you can send to an ISP. If recipients mark your emails as spam, regardless of the content, it severely impacts your sender reputation. This is why list hygiene and sending relevant content to an engaged audience are paramount. Even if you offer something free, if it feels misleading or unwanted, it can lead to complaints.
Focusing on delivering value and maintaining a clean, engaged list will do more for your deliverability than meticulously avoiding a few keywords. If you're struggling with emails going to spam, consider factors beyond just content, such as why your emails are going to spam.
Misleading offers: If the offer of 'free' is deceptive or requires unforeseen costs, it can lead to negative recipient feedback.
Excessive bolding or capitalization: Overusing visual emphasis, especially with words like 'FREE', can still trigger filters or annoy recipients.
Poor sender reputation: A history of low engagement or high spam complaints will amplify the impact of any potentially problematic word, including 'free.'
Best practices for using promotional language
While the impact of 'free' has diminished, it's still wise to use it thoughtfully. The key is to ensure your offer is genuinely valuable, transparent, and aligned with your brand's overall messaging. Don't try to trick recipients with false promises of something free, as this will quickly backfire and damage your sender reputation.
Consider the Federal Trade Commission's guide concerning the word 'free'. Misleading promotions can lead to consumer complaints and regulatory issues, which will certainly impact your email program. Honesty and clarity are always the best policies when it comes to promotional language.
Ultimately, your goal is to land in the inbox and engage your audience. This means prioritizing relevant content, maintaining a healthy sender reputation, and fostering positive interactions. The word 'free' can be a powerful motivator when used responsibly and as part of a well-rounded email strategy. For more details on keywords, refer to what are spam trigger words.
Views from the trenches
Best practices
Maintain strong sender reputation through consistent good practices.
Segment your audience to send highly relevant content.
Use email authentication like SPF, DKIM, and DMARC.
Ensure the offer in your email is genuinely free and transparent.
Monitor your engagement rates, especially opens and clicks.
Common pitfalls
Sending to unengaged or purchased lists, leading to high complaints.
Over-promising and under-delivering on 'free' offers.
Excessive capitalization or exclamation marks with 'free'.
Ignoring DMARC reports which provide valuable deliverability insights.
Not monitoring for blocklist (or blacklist) listings.
Expert tips
A/B test subject lines with and without 'free' to see what resonates with your audience.
Focus on the value proposition rather than just the word 'free'.
Combine 'free' with other strong action-oriented words.
Ensure your email's body content supports the 'free' offer clearly.
If using 'FREE' in all caps, ensure your sender reputation is impeccable.
Marketer view
Marketer from Email Geeks says they recently saw a client email with three text links containing 'FREE' that resulted in over a 50% bounce rate from major ISPs such as AOL, Yahoo, and Hotmail.
2019-07-26 - Email Geeks
Expert view
Expert from Email Geeks says they have not seen issues with the word 'free' when it is used appropriately, as sophisticated spam filters consider much more than just the word itself, focusing on context and avoiding misleading information.
2019-07-27 - Email Geeks
The new reality of 'Free' and email deliverability
While the myth of 'free' as an automatic spam trigger has largely been debunked by the advancement of spam filtering technologies, its usage still requires careful consideration. The context in which the word is used, your overall sender reputation, and most importantly, recipient engagement, are the primary drivers of deliverability.
Instead of obsessing over single words, focus on building a strong, trustworthy sending profile. This includes proper email authentication, maintaining clean and engaged subscriber lists, and consistently providing valuable content. When these foundational elements are in place, you can use 'free' confidently, knowing your emails are more likely to reach the inbox and achieve their intended purpose.
Gmail and 
Yahoo look at a holistic view. They consider factors such as your sending volume, bounce rates, spam complaint rates, and engagement rates (opens, clicks). A legitimate offer of something free, if it aligns with your audience's expectations and your sending history, is unlikely to be penalized.
