Deliverability insights
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Mailchimp to Brevo Migration: Deliverability Pitfalls and How to Test
Mailchimp's reputation is yours alone, Brevo's is shared with their pool. Migrating means new IP, new sub-IP rotation, new authentication. The specific Mailchimp→Brevo gotchas.
Switching ESPs Without Killing Deliverability: The Migration Playbook
A naive cutover from one ESP to another tanks inbox rate for 4-6 weeks. The graduated migration playbook: dual-send, IP warmup, DNS staging.
Tax Season Email Deliverability: Accountants and Financial Services
January-April sees accountants drowning their clients in 'send your W-2' reminders. Filters react: financial keywords + attachment risk = spam. The tax-season playbook.
Back to School Emails: Education Sector Deliverability Guide
Education senders hit volume spikes in late July through August. Edu domains get extra filter scrutiny. The deliverability rules specific to schools, ed-tech, and tutoring.
New Year Email Campaigns: Warm Up Before the Rush
January 2nd through 7th sees the year's largest cold-email surge. If you start sending then with a cold domain, you fight every other sender for attention. Warm in December.
Holiday Season Emails: Why December Is the Hardest Month for Inbox
Volume across all senders triples in December. Filters get stricter. Engagement drops. Why the inbox is hardest 12-15 to 12-26 — and how to plan around it.
Black Friday Email Deliverability: Pre-Campaign Checklist
BFCM volumes 5-10x normal. Without warm-up, segmentation, and a seed-test rehearsal in October, your Cyber Monday email lands in Promotions or worse.
Purchased Email Lists: Why They Destroy Deliverability (With Data)
Bought lists carry 30-60% bad addresses, violate GDPR/CAN-SPAM/CASL, get ESP accounts banned within hours, and cost months to recover from. The full math, plus legitimate alternatives.
Re-Engagement Campaigns: How to Reactivate Dead Contacts Without Hurting Deliverability
A blast to dormant contacts can crash reputation overnight. The safe playbook: stratify by inactivity, send small batches from a separate identity, single attempt only, ruthless suppression.
Spam Traps Explained: How One Bad Address Ruins Your Domain
Pristine, recycled and typo traps — who runs them, how they enter your list, why verifiers can't catch them all, and why a sunset policy is the only complete defence.
Email Verification Services Compared: ZeroBounce vs NeverBounce vs Bouncer
Honest comparison of the four major verifiers — coverage, catch-all handling, EU/GDPR posture, false-positive rates and which to use for which job.
Email List Hygiene: Why Cleaning Your List Improves Inbox Placement
A clean 50K list out-delivers a dirty 100K every time. The hygiene playbook: bounce handling, suppression, sunset policies, complaint feedback loops, segmentation by engagement.
Email Subject Line and Spam: Do Caps and Emojis Hurt Deliverability?
All-caps still costs 8-12% inbox placement. One emoji helps, three hurts. Faking RE: prefixes is detected. The real subject-line rules backed by seed-mailbox testing.
Attachments in Email: PDF, DOCX, ZIP — Which Triggers Spam?
The risk hierarchy from blocked-outright (.exe) through password-protected ZIP penalties to generally-safe PDF — and why cloud links beat attachments for cold outreach every time.
Links in Email: How Many Is Too Many for Spam Filters
Filters score every link's domain reputation, redirect chain, and anchor mismatch. Why 5 clean links beat 2 dirty ones, and why generic shorteners and shared trackers cost you placement.
Image-to-Text Ratio in Email: Does It Still Affect Spam Filters?
The 60/40 rule is dead but the principle survives. Modern filters OCR your images, score alt text, penalise image-only emails — and the working ratios for B2B and B2C in 2026.
HTML Email vs Plain Text: Which Gets Better Inbox Placement?
Plain-text-only is a 2008 myth and HTML-only is suspect. Multipart/alternative with both parts properly populated is the modern baseline — here's the spec, the rendering rules and the test data.
Spam Trigger Words 2026: Which Still Matter and Which Are Myths
Modern Bayesian and ML filters score sender reputation, engagement and link quality far more than vocabulary. The handful of words that still hurt — and the long list of myths — explained with real test methodology.
I'm on 5 Blacklists at Once: Triage Guide (Which to Fix First)
Multi-list listings almost always share one root cause. Triage by impact — Spamhaus and Microsoft first, Barracuda and SpamCop next, niche RBLs last — with a time-cost vs impact matrix and signals for when to give up on a domain.
Microsoft SNDS: How to Check and Fix Your IP Reputation With Outlook
Microsoft SNDS gives per-IP daily reputation data nobody else can see — registration via TXT record, the Green/Yellow/Red colour codes, fixing Red status, JMRP feedback loop, and why SNDS doesn't cover Office 365.
UCEProtect Blacklist: The Controversial List That Blocks Entire Subnets
UCEProtect Level 1/2/3 explained, with the collateral-damage problem of Level 3 listing entire ASNs, the €15 paid express delisting option, and a pragmatic view on which receivers actually query Level 2/3.
Spamcop Blacklist Removal: Why It's Automatic (and Why That's a Problem)
SCBL listings auto-expire 24h after the last spam report — so there's no removal form. Explains the re-listing trap caused by forwarding loops, seed traps and reporting users, and the detective work that breaks the cycle.
SORBS Blacklist: How to Delist and Prevent Re-Listing
SORBS sub-lists (DUHL, SPAM, ZOMBIE, OPEN-RELAY) explained, with historical delisting workflow and a candid note that Proofpoint sunset SORBS in mid-2024. Covers what 2026 SORBS-attributed bounces actually mean and the modern equivalents.
Barracuda Blacklist Removal: Request Form + What to Fix First
Barracuda BRBL blocks at thousands of business mailboxes. Walks through the removal request form, what to write in the explanation, and what list-quality / authentication issues to fix before submitting.
How to Delist From Spamhaus: Step-by-Step (SBL, XBL, PBL)
Spamhaus delisting playbook by list type — SBL needs a manual form with evidence, XBL is automatic via CBL self-service, PBL is ISP-controlled. Includes the lookup tool, what evidence to prepare, and realistic 24-72h response times.
Domain Warmup Failed: Signs, Causes, and How to Restart
Symptoms of a failed warmup, the five most common root causes, and the rules for deciding whether to recover the damaged domain or restart on a fresh one.
Buying a Used Domain for Cold Email: How to Check Its Reputation First
Used domains carry their old reputation. The full due-diligence checklist: WHOIS history, Wayback, SecurityTrails DNS, blacklists, and a probe-with-control before paying.
How to Test If Your Warmup Actually Worked (Seed Test After Warmup)
Why warmup tools' self-reported numbers lie, and how to verify with three staggered seed tests against 20+ real provider mailboxes before launch.
IP Warmup for Dedicated Senders: Volume Ramp-Up Schedule
A real day-by-day volume schedule for warming a dedicated IP, with per-provider caps for Gmail, Outlook, Yahoo, and recovery rules when 4xx deferrals appear.
Domain Age and Deliverability: How Long Until Gmail Trusts You
Why WHOIS age is a myth and what Gmail actually tracks. Real reputation milestones at days 30, 90, and 180, plus what bends the curve.
Unsubscribe Link: Legal Requirements by Country (US, EU, CA, UK, RU)
Every country requires unsubscribe — they disagree on speed, format, and link lifetime. A side-by-side reference for global senders, plus the RFC 8058 one-click rule that beats them all.
Can You Legally Send Cold Email in EU? GDPR + Legitimate Interest Explained
B2B cold email in the EU lives in a narrow legitimate-interest lane — and disappears entirely in Germany. How to write a balancing test that actually holds up at a DPA.
CASL: Canadian Anti-Spam Law for Email Senders (Practical Guide)
Canada's anti-spam law is the strictest in North America: opt-in by default, 2-year implied-consent window, and CRTC penalties up to CAD $10M per violation for businesses.
GDPR and Email Marketing: Consent, Deliverability, and the Fine Print
GDPR is a data-protection law that quietly governs every email campaign. Lawful bases, consent vs legitimate interest, soft opt-in, and how privacy posture moves your inbox rate.
CAN-SPAM Act 2026: What Email Senders Must Do (and What Most Get Wrong)
The US CAN-SPAM Act in plain English: required disclosures, the 10-business-day opt-out clock, and the $50,120-per-email penalty most senders forget exists.
Email Is Not Dead — Your Metrics Are
Every year someone declares email dead. Every year email outperforms the channel that replaced it. The thing that died is the honesty of the metrics we used to measure email.
The CMO Who Killed Their Email Team's Dashboards and Saw Revenue Go Up
A composite story from half a dozen conversations: what happens when you turn off the open-rate dashboards and force a team to use only placement, replies and pipeline.
Why Most Email Marketing Agencies Are Selling You Vanity
A provocation: the email agency industry has quietly become a vanity-metrics machine. What you are paying for, what you are actually getting, and what you should demand.
Apple Mail's Opaque Filtering: Probing Without Feedback Loops
Apple has no Postmaster, no FBL, no reputation dashboard, no complaint feed. Here's how to reverse-engineer Apple Mail placement with only indirect signals.
Microsoft SNDS and Why Most Senders Misread It
SNDS is a green dashboard that hides a red problem. Four reasons senders misinterpret Microsoft's smart network data, and what to do instead.