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Spam Words That Kill Email Deliverability in 2026

May 6, 2026

Spam filters have changed a lot over the past decade. Modern filters from Google, Microsoft, and the major ESPs use machine learning, sender reputation scoring, engagement signals, and content analysis together, not a simple blocklist of forbidden words. But word choice still matters. Certain phrases are so strongly associated with spam that they function as reliable signals even in sophisticated models, and avoiding them is still one of the fastest ways to improve deliverability.

How spam filters actually work in 2026

Before getting into specific words, it’s worth understanding what you’re actually up against. Modern spam filters evaluate:

  • Sender reputation: your domain’s sending history, IP reputation, and complaint rate
  • Authentication: whether your emails pass SPF, DKIM, and DMARC checks
  • Engagement signals: open rates, click rates, and how many recipients mark your emails as spam
  • Content analysis: the text of your email, subject line, HTML structure, image-to-text ratio, and link domains
  • List hygiene: bounce rates and the quality of your subscriber list

Word choice is one input among many. A strong sender reputation can help you survive occasional use of risky phrases. A weak reputation means even clean copy gets filtered. But if you’re doing everything else right, certain words still move the needle in the wrong direction.

Subject line phrases to avoid

Subject lines get the most scrutiny because they’re evaluated before the email body. These phrases are consistently associated with high spam rates:

Financial urgency

  • Free, FREE (especially in all caps)
  • Earn $, Make money, Extra income
  • No cost, No fees, Zero risk
  • 100% free, Absolutely free
  • Cash, Prize, Winner, You’ve been selected

False urgency and pressure

  • Act now, Limited time, Expires today
  • Don’t delete, Don’t ignore, Last chance
  • Urgent, Important notice, Final notice
  • While supplies last

Exaggerated claims

  • Guaranteed, 100% guaranteed
  • Amazing, Incredible, Unbelievable
  • Once in a lifetime, Never before
  • Best price, Lowest price, Cheapest

Deceptive framing

  • Re: (when it’s not a reply)
  • Fw: (when it’s not a forward)
  • As per our conversation (without a prior conversation)

Body copy phrases that trigger filters

Medical and legal

  • Cure, Miracle, Breakthrough
  • Lose weight fast, Burn fat
  • Lawyer, Legal, Settlement, Lawsuit
  • Prescription, Medication, Pharmacy

Financial

  • Get out of debt, Eliminate debt
  • Credit repair, Improve your credit
  • Investment opportunity, Double your income
  • Stocks, Trading, Forex, Cryptocurrency (in cold outreach contexts)

Generic spam patterns

  • Click here (replace with descriptive link text)
  • Visit our website (overly generic)
  • This is not spam (the surest way to look like spam)
  • Unsubscribe (fine in the footer; avoid using it in body copy to emphasize removal)
  • If you no longer wish to receive (phrased as filler rather than a clear unsubscribe link)

HTML patterns that look like spam

Spam filters analyze your HTML, not just your copy:

  • All-caps text: aggressive formatting is a common spam signal
  • Excessive exclamation marks: one or two is fine; several per email is not
  • Very high image-to-text ratio: image-only emails have low text content, which is a red flag. Include sufficient plain text.
  • Tiny or hidden text: white text on a white background, 1px font sizes, display:none on content
  • Mismatched link domains: display text says one URL, the actual href goes somewhere else
  • Shortened URLs: bit.ly and similar services are heavily associated with phishing

What to do instead

Replace vague urgency with specific deadlines. “Sale ends Sunday at midnight” is both honest and effective. “Limited time offer” is neither.

Describe links with action verbs. “Read the case study,” “Download the guide,” “View your invoice”: all better than “click here.”

Let your value proposition do the work. If you’re offering something genuinely useful, you don’t need to inflate the language. Spam language exists because bad offers need to be hyped. Good offers don’t.

Use the spam scanner before you send. SendReady’s Spam Word Scanner checks your email copy against a current list of deliverability-killing phrases, flagging them by severity so you can revise before you hit send.

  • Spam Word Scanner: Scan your email copy for phrases that trigger spam filters.
  • CSS Inliner: Ensure your HTML renders correctly across all email clients.
  • HTML Minifier: Keep your email under Gmail’s 102KB clip threshold.