Blog
Email-verification, deliverability, and ESP-integration writing — practical pieces for the kind of person who reads /v1/check response shapes for fun.
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Operator fingerprint clustering disposable email
One operator runs 14 'different' temp-mail brands with the same AdSense, GA4, GTM IDs. The fingerprint clustering methodology that maps disposable email operators.
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Bulletproof hosting disposable email
186 operator IP /24 ranges host the back-end of disposable email networks. Linode, Hetzner, OVH, Leaseweb cluster heavily. The CIDR map nobody publishes.
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Scraping 1secmail mail.tm mail.gw inbox domains
1secmail, mail.tm, mail.gw publish their inbox-domain rotation via public APIs. We scrape all three daily to catch every domain they hand out.
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Disposable email false positives: 380-domain allowlist
Pure pattern-matching disposable detection over-blocks gmail.com, harvard.edu, gov.uk. Our 380-entry allowlist wins over any blocklist. Categories explained.
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CT-log scanner disposable email detection
We poll crt.sh hourly for new TLS certs matching disposable-mail patterns. New throwaway providers are in our database 4 hours after their first cert.
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Numbered MX rotation disposable detection
Disposable operators rotate mx1, mx2, ..., mx99 to evade blocklists. The 12 parent-MX regex patterns we use to catch them before they're listed anywhere.
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Cloudflare-fronted disposable detection
5,258 disposable mail domains hide behind Cloudflare so MX probes fail. The signal stack that detects them anyway: 'weighted-disposable' verdict explained.
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Yopmail empire: 4 brands, 654 domains
Yopmail runs 4 brands (yopmail.co, temp-inbox.com, daymail.com, hidemyemail.com) and 654 disposable email domains. We traced them via MX cluster. The receipts.
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The 638 operators behind disposable email
We classified 265,673 disposable mail domains into 638 distinct operators. Top 10 operators control 58% of all domains. The operator graph nobody publishes.
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The alias forwarder trick: 707 forwarding domains
707 disposable domains aren't disposable — they're alias forwarders that route your signup confirmation into a real Gmail inbox the operator controls. Mechanism, named examples, signup-form fix.
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Free Email Verification API: What "Free" Means in 2026
Most "free" email verification APIs are 100-credit one-time trials, not free tiers. Here's what each provider actually gives you free, and which one survives past day one.
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How to Pick an Email Verification API in 2026
7 things that actually matter when picking an email verification API — pricing model, p50 latency, bounce-feedback loop, verdict semantics. With a real evaluation script you can run in 10 minutes.