Email Spam Word Checker
Subject line spam filters run before a human ever reads your email. Words like "free," "guaranteed," or "urgent" — even in legitimate campaigns — raise filter scores. Paste your subject line and see exactly what's triggering filters and safer alternatives.
Also works for preheader text and email preview snippets
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Flagged Words & Alternatives
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How Spam Filters Actually Score Your Subject Line
Spam filters at Gmail, Outlook, and Yahoo use hundreds of signals to classify emails — and subject line content is one of the most heavily weighted. Certain words and phrases have become strongly associated with spam campaigns: urgency triggers, financial promises, excessive punctuation, and specific power words that marketers have overused to the point of toxicity.
It's not just the word itself that matters — it's the context, frequency, and combination. "Free" in a subject line from a trusted sender with good engagement is rarely a problem. "FREE PRIZE — Act Now!!!" from a domain with poor reputation triggers every filter in sequence. This tool flags the highest-risk terms so you can make informed decisions before you send.
Subject line length sweet spot
40–60 characters performs best across most clients. Gmail shows ~60 characters on desktop, ~45 on mobile. Outlook shows fewer. Keep critical information front-loaded.
ALL CAPS triggers spam filters
Excessive capitalization is one of the oldest spam signals. One or two capital words for emphasis is acceptable — entire phrases in caps looks promotional and suspicious.
Punctuation overuse is scored
Multiple exclamation marks (!!!) and question marks (???) are heavily penalized. Use one, or none. Punctuation should serve clarity, not simulate urgency.
Context matters as much as words
Spam filters weigh subject line content alongside sender reputation, engagement rates, and domain age. A pristine subject line won't save a spam-flagged domain.
Related Free Tools
Spam Words Are One Problem. Subject Line Deliverability Is the Other.
Even a clean subject line won't reach the inbox if your sender reputation is low. InboxEagle monitors inbox placement for your exact sending domain across major ISPs — so you know whether your emails are reaching the inbox or not, regardless of subject line.
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