Email SubjectOpen RatePower WordsSpam CheckA/B TestingFree ScorerEmail SubjectOpen RatePower WordsSpam CheckA/B TestingFree Scorer

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8-Factor Score · Spam Check · Open Rate Tips

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Best Practices

FactorGuideline
Length41-50 characters (6-10 words) is the sweet spot
Mobile previewFirst 30 chars must hook — most inbox cutoff
PersonalizationUsing first name increases open rate 20%+
Urgency"Today only," "Last chance" (but don't overuse)
Curiosity gapCreate intrigue without being clickbait
Numbers"5 ways to..." outperforms vague subjects
Emoji1 emoji can boost opens 5-10% (test it)
Avoid ALL CAPSTriggers spam filters + looks aggressive

Spam Trigger Words

CategoryWords to Avoid
MoneyFREE, $$$, cash, earn, income, million, winner
Urgency (spammy)ACT NOW, limited time, don't miss, expires
HypeAmazing, incredible, guaranteed, no obligation
ShadyClick here, congratulations, dear friend

Using 1-2 isn't fatal, but stacking multiple spam words drops deliverability significantly.

Subject Line Formulas

FormulaExample
How to [achieve X]How to double your email open rates
[Number] ways to [Y]7 ways to save on your next trip
Don't [do X] until [Y]Don't buy a laptop until you read this
[Name], [personalized]Sarah, your cart is waiting
Question formatAre you making these 3 resume mistakes?
Curiosity gapThe one thing top performers never do