Email Spam Triggers & Keywords:
Words That Trigger Filters

SpamAssassin Scoring System

SpamAssassin is the open-source spam filter used by many ISPs and ESPs. It assigns point values to various spam indicators. Emails scoring above 5 points are typically flagged as spam; 5-10 points trigger heavy filtering. Common point values range from 0.5 to 3 points per trigger.

Major ISPs like Gmail and Yahoo use SpamAssassin-like rules alongside machine learning. A high spam score doesn't guarantee filtering—it's one factor among many. However, reducing spam score always improves deliverability odds.

SpamAssassin Score Breakdown (typical scoring):

• 0-5 points: Low risk (likely inbox)
• 5-8 points: Elevated risk (may trigger filtering)
• 8+ points: High risk (likely spam folder)

Each trigger rule in SpamAssassin can add between 0.3 and 3 points. For example, the phrase "FREE" alone adds ~0.5 points, but using it multiple times compounds. Hidden text detection (color:white on white:background) adds ~2.5 points.

Spam Trigger Keywords

Words trigger filters based on context, frequency, and combination with other factors. Using a single trigger word isn't catastrophic, but combining many raises red flags significantly.

High-Risk Keywords (1-2+ points each):

• FREE (especially all caps)
• URGENT
• Limited Time / Act Now
• Buy Now / Purchase Now
• Risk Free / No Risk
• Guarantee / Guaranteed
• Winner / Claim Prize
• No Credit Card Required
• Unsecured Debt / Bad Credit
• Congratulations / You've been selected

Medium-Risk Keywords (0.5-1 point):

• Click Here
• Order Now
• Apply Now
• Schedule Consultation
• Limited Spots
• Exclusive Offer

Alternative Phrasing: Instead of "FREE," use "No cost," "Included," or "Complimentary." Instead of "URGENT," use "Time-sensitive," "Expiring soon," or "Ending Friday." These convey urgency without triggering spam rules.

Punctuation & Capitalization Analysis

Excessive punctuation is a classic spam indicator. Legitimate business emails use restrained punctuation; scams use multiple exclamation marks and question marks to create false urgency.

Punctuation Violations:

• 3+ exclamation marks in a row (!!! or worse): ~1.5 points
• 3+ question marks (???) : ~1 point
• Mixed punctuation (!!!???) : ~2 points
• ALL CAPS subject line: ~1.5 points
• ALL CAPS body text (more than 3 words): ~1 point per instance

Safe Practices: Use single punctuation marks. ONE exclamation mark max per paragraph. Subject line in title case or sentence case, not all caps. Avoid excessive caps even in headings—use bold formatting instead.

Font Size & Color Triggers

Deceptive formatting is heavily penalized. Hidden text (white text on white background), extremely large fonts, or invisible text all signal fraud.

Format Red Flags:

• Hidden text (color matches background): ~2.5 points
• Font size over 36px in body text: ~0.5 points
• Blinking/flashing text (via CSS): ~1.5 points
• Tiny font under 10px (unreadable): ~1 point

Best Practice Sizes:

• Body text: 14-16px
• Subheadings: 18-20px
• Main heading: 24-32px

Color Contrast: Always maintain readable contrast. WCAG AA standard requires 4.5:1 contrast ratio for body text. Dark text on light background or vice versa is safe.

Image-to-Text Ratio

Emails that are 100% image (no text) are red flags. Spam often uses image-only designs to evade text-based filtering. Maintain a healthy text-to-image balance.

Ratio Guidelines:

• Minimum 40% text, 60% image: Safe
• 25-40% text, 60-75% image: Borderline
• Under 25% text: High risk (~1.5 points)
• 100% image (no alt text): ~2 points

Rule of Thumb: If you remove all images from an email, the remaining text should still make sense and be 150-300 words minimum.

Image Best Practices: Always include descriptive alt text. Use images to enhance, not replace, text. Include a text footer with links (even if header is image-based).

Link-to-Text Ratio

Excessive linking (every line is clickable) appears deceptive. A healthy email balances narrative text with strategic links.

Link Scoring:

• 20-30% of content is links: Safe
• 30-50% of content is links: Borderline (~0.5 points)
• Over 50% of content is links: High risk (~1.5 points)

Example (Risky):

Example (Safe):

HTML Formatting Red Flags

Malformed HTML, missing closing tags, and excessive comments all signal low-quality or automated spam. Clean, valid HTML improves deliverability and rendering.

Common HTML Violations:

• Unclosed tags (missing </p>, </div>): ~0.5 points
• Embedded JavaScript: ~2 points (often blocked outright)
• Excessive HTML comments (<!-- -->): ~0.5 points
• Deprecated tags (e.g., <font>, <center>): ~0.3 points
• Inline CSS with !important excessive use: ~0.3 points

Safe HTML Practices: Use table-based layouts (still best practice in email). Close all tags properly. Avoid JavaScript entirely (won't execute in email). Use inline CSS, not <style> blocks. Test in Litmus or Stripo to validate rendering.

Monitoring Your Spam Score

Before sending any campaign, scan your template for spam score. Use free tools or professional services to get detailed feedback.

Free Tools:

• Mail Tester – Free spam score report
• Postmark Spam Check – Detailed SpamAssassin breakdown
• InboxEagle Spam Checker – Real-world inbox placement + score

Ideal Workflow:

1. Create template with best practices in mind
2. Scan spam score before finalizing copy
3. Adjust high-risk words or formatting if score is 5+
4. Run seed list test with InboxEagle to check real inbox placement
5. Monitor engagement on first send (low engagement + deliverability issues = reputation damage)

Ongoing Monitoring: Track spam complaint rate. Any spike above 0.1% requires immediate investigation. Check your DMARC/SPF reports for alignment failures. Monitor open and click rates for sudden drops (indicator of spam folder migration).