B
Evidence Grade B
Graded
under review
Safe to Cite
Current
30%
30% -- reply rate reduction for Emails with all caps subject lines (2026)
Attribution:
View source
Lighthouse Research Team
Last verified:
·
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Source verified
Evidence graded
Value
30%
Unit
Percentage
Data Vintage
2026
Entity
Evidence Quality
B
Strong, reliable evidence
Sourced from a well-regarded research firm or industry leader with transparent methodology and a reasonably large sample.
Single source - not yet corroborated
Score breakdown
Extraction
75
Source Trust
60
Citation Chain
20
Independence
30
Methodology
45
Freshness
95
Source
Boomerang
Primary
Tier B
https://unlayer.com/blog/11-bad-email-design-mistakes-youre-making ↗
Source Article
11 Bad Email Design Mistakes You’re Making
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Original Research
Boomerang
· Original study ↗
Methodology
Boomerang study on subject line capitalization and reply rates
Methodology documented
Segmentation
Industrymarketing
Cite this stat
Plain Text
Emails with all caps subject lines: 30% reply rate reduction. Source: Boomerang (2026). Via Lighthouse Intelligence -- https://lighthousedata.io/data/all-caps-subject-reply-rate-drop
HTML Embed
<blockquote cite="https://lighthousedata.io/data/all-caps-subject-reply-rate-drop" style="border-left:3px solid #2563eb;padding:12px 16px;margin:16px 0;font-family:system-ui,sans-serif;background:#f0f4ff;"><strong>30%</strong> -- reply rate reduction for Emails with all caps subject lines<br><small>Source: Boomerang (2026) · <a href="https://lighthousedata.io/data/all-caps-subject-reply-rate-drop" target="_blank" rel="noopener">Lighthouse Intelligence</a></small></blockquote>
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