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MailTools

Email Subject Line Checker

Analyze your subject line for length, spam trigger words, and preview how it appears on mobile devices.

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Try examples:

straightenLength Analysis

Character count0 / 50 ideal
Word count0 words

previewPreheader Analysis

Character count0 / 40-100 ideal
Tip: Preheader text appears after your subject line in the inbox. Use it to add context and encourage opens.

shieldSpam Check

Enter a subject line to check for spam trigger words.

lightbulbBest Practices

  • checkKeep it under 50 characters for best mobile display
  • checkPut important words at the beginning
  • checkAvoid ALL CAPS and excessive punctuation!!!
  • checkPersonalize when possible (name, location)
  • checkCreate urgency without being spammy

smartphoneMobile Preview

See how your subject line appears in mobile email clients.

phone_iphoneiPhone (375px)
androidAndroid (360px)
computerDesktop
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Your Company9:41 AM
Your subject line preview...
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