B
Evidence Grade B
Graded
accuracy verified by the review judge
Safe to Cite
Dated
21%
21% -- email inbox delivery failure rate for US ISPs (2009)
At US ISPs, 21% of permission-based emails sent to the ReturnPath probe network did not make it to the inbox.
Attribution:
View source
Lighthouse Research Team
Last verified:
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Source verified
Evidence graded
Value
21%
Unit
Percentage
Data Vintage
2009
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
ReturnPath
Primary
Tier B
http://blog.wordtothewise.com/2009/07/delivery-metrics/ ↗
Source Article
Delivery Metrics
Original Research
ReturnPath
· Original study ↗
Methodology
ReturnPath probe network measurements at US ISPs; 3% to bulk folder, 17% not delivered at all
Methodology documented
Segmentation
Industrymarketing
Cite this stat
Plain Text
US ISPs: 21% email inbox delivery failure rate. Source: ReturnPath (2009). Via Lighthouse Intelligence -- https://lighthousedata.io/data/returnpath-us-isps-inbox-failure-2009
HTML Embed
<blockquote cite="https://lighthousedata.io/data/returnpath-us-isps-inbox-failure-2009" style="border-left:3px solid #2563eb;padding:12px 16px;margin:16px 0;font-family:system-ui,sans-serif;background:#f0f4ff;"><strong>21%</strong> -- email inbox delivery failure rate for US ISPs<br><small>Source: ReturnPath (2009) · <a href="https://lighthousedata.io/data/returnpath-us-isps-inbox-failure-2009" target="_blank" rel="noopener">Lighthouse Intelligence</a></small></blockquote>
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