Does using spammy words put you in spam?
Still have a question, spotted an error, or have a better explanation or a source we should cite?
Myth: Mostly False. You've probably heard that writing "FREE!!!" or "Buy now" in your subject line will send your email straight to spam. It's one of the most repeated pieces of email advice out there. It's also mostly wrong.
Modern spam filters don't work like a list of forbidden words. They use machine learning to look at hundreds of signals at once. Your word choice is just one tiny piece of that picture.
What filters actually weight heavily are things like your sender reputation, whether your domain passes authentication checks (SPF, DKIM, DMARC), and how your subscribers engage with your emails over time. A sender with a solid reputation and real engagement can write "free offer inside" without much consequence. An unknown sender with no authentication and a cold list might get filtered even with the most neutral subject line imaginable.
The keyword myth dates back to early spam filters from the late 1990s and early 2000s. Those systems genuinely did scan for word patterns. Filters have moved on. Most senders haven't updated their mental model to match.
That said, context still matters. Overly hypey copy in combination with other weak signals (low engagement, missing authentication, high complaint rates) can tip the balance. It's not that the words triggered the filter. It's that the words fit a pattern the filter associates with low-quality sending.
So don't obsess over your word choices. Focus on the signals that actually move the needle: clean authentication, a healthy list, genuine engagement, and a consistent sending history. Get those right, and your copy has a lot more room to breathe.
If you want to test a subject line before sending, our free Subject Line Tester can flag anything that looks risky.
Contributors
Who worked on this answer
Every name links to their profile. Every company links to their site. Real people, real accountability.
