Reference

Securing a domain portfolio against hijacking, lookalike/cousin-domain abuse, and spoofing — inventory, registrar/registry locks, defensive registration, monitoring, takedown paths, and the protective DNS records for non-sending and parked domains.

Dated, vendor-attributed benchmark tables — Validity seed-measured inbox/spam/missing rates by provider, country, region, and industry; Marigold and Freshworks per-industry engagement rates; and Sinch's sender-adoption and maturity figures.

Annotated guide to the key independent deliverability expert sites — Word to the Wise, Spam Resource, EmailKarma — and how to use them for current events.

Alphabetical one-stop definitions of the deliverability terms of art used across this knowledge base, with links to the deep articles.

A practical catalog of free diagnostic tools — aboutmy.email, mail-tester, learndmarc, internet.nl, Google CheckMX, MXToolbox Email Health, check.spamhaus.org — what each tests, inputs, and where it fits in a workflow.

How DNSBLs work, the Spamhaus blocklists (SBL/CSS/XBL/PBL/DBL/ZRD/AuthBL/HBL, combined as ZEN), why senders get listed, how delisting works, and Spamhaus's operational deliverability guidance.

The classification layer for the abuse cluster — one entry per abuse type with definition, victim, the detection signals an ESP sees, the typical actor (intentional customer vs compromised customer vs external), and which KB article owns the response.

The industry-consensus stance — deceptive delivery of unsolicited "cold email" is an abusive practice; full definition, deceptive-tactic list, detection indicators, and the non-transferability of consent.

The OECD's cross-border anti-spam policy framework: eight elements, the Council Recommendation on enforcement co-operation, and the BIAC/MAAWG ISP and email-marketing best practices.

BGP/IP hijacking and the IPv4 transfer/leasing market as email-abuse vectors — how spammers acquire fresh "clean" IP space, the research quantifying transferred/leased-prefix abuse, Spamhaus's network-hijacking observations, and RPKI/ROA as the mitigation.

The two surviving commercial allowlist programs — Validity Sender Certification and the Certified Senders Alliance — with exact admission criteria, performance thresholds, costs structure, which receivers honor each, and an honest assessment of when certification pays off.

Trap types (pristine, recycled, typo), how each gets onto a list, what hitting them signals about data quality, and how to respond.

Per-list detail on Spamhaus listing criteria, escalation policy, self-service vs investigated delisting, return/error codes, and how receivers should query the zones — beyond the zone overview in Blocklists & Spamhaus.

How modern content filters judge message bodies — URL/domain reputation lists (SURBL zones, query mechanics, redirector handling) and fuzzy hashing (rspamd shingles, near-duplicate campaign detection) — and what that means for senders' link domains and templates.