Half-Year Review: Email in the AI Inbox Era
Six months that rearranged the reading layer: Gemini in Gmail, Microsoft rejecting outright, DMARC finally a standard. What the first half of 2026 means for senders.
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Deliverability Postmortems: Learning From Incidents
The incident is over, placement recovered, and the pressure to move on is enormous. The blameless postmortem practice that converts each incident into prevention.
Writing for AI Readers: Structure When Gemini Summarizes You
Five months of AI Overviews data shows opens up and clicks down: recipients read summaries. How to structure email so the model's version still does your job.
Backscatter: The Bounces You Never Sent
When spammers forge your domain as their envelope sender, the bounces come to you. What backscatter is, why it happens, and how to stop causing and receiving it.
DMARCbis Is Published: What RFC 9989 Changes
After eleven years, DMARC is a real standard: RFC 9989, 9990, and 9991 replace RFC 7489. What is different, what stays, and the short list of actions for senders.
Per-Provider Playbooks: Operating Gmail, Microsoft, and Yahoo Differently
The big three score senders differently, expose different data, and fail in different ways. One operating playbook per provider beats one averaged strategy.
Subaddressing: What Plus Addresses Tell Senders
user+anything@gmail.com is one mailbox wearing labels. How subaddressing works, why blocking it backfires, and what plus addresses reveal about your data flows.
DNSSEC for Email Operators: Worth It, and How Not to Break Everything
Every email trust decision resolves through DNS, and DNSSEC is what makes those answers tamper-proof. What it buys email, what DANE requires, and safe operations.
Transactional Latency: Measuring Time-to-Inbox
For OTPs and password resets, seconds are the metric. Where latency hides in the sending path, how to measure time-to-inbox honestly, and what budgets to hold.
Preference Centers That Prevent Unsubscribes
A preference center offers frequency and topic choices to people about to leave. Where it genuinely saves subscribers, where it violates one-click rules, and the design that works.
Rebrand Migrations: Moving Email Identity to a New Domain
A rebrand replaces the one asset deliverability cannot: your domain's history. The parallel-running plan that carries trust from the old name to the new one.
Bot Clicks and Link Scanners: Cleaning Your Click Data
Security gateways click every link in every email before humans see them. How scanner traffic pollutes click metrics, breaks one-click flows, and how to filter it.
Microsoft's Rejection Phase Is Live: A 550 5.7.515 Field Guide
Outlook now hard-rejects non-compliant bulk mail with 550 5.7.515, and Safe Senders cannot override it. Diagnosing the bounce and fixing the authentication behind it.
Gmail Enters the Gemini Era: AI Overviews and the AI Inbox
Gmail's January update puts Gemini between senders and readers: thread summaries, an AI-prioritized inbox, and suggested replies. What changes for email programs.
The Annual Deliverability Audit: A January Checklist
January is the quiet window between peak seasons. The full-stack audit that catches drift in authentication, DNS, list hygiene, and monitoring before it costs mail.
2025 in Email: The Year Authentication Became Mandatory Everywhere
Microsoft joined the mandate, Gmail moved to hard rejection, and DMARCbis reached the finish line. What 2025 changed for senders and what it sets up for 2026.
Greylisting, Tarpitting, and Other Receiver Defenses Senders Should Understand
Receiving servers defend themselves with deliberate delays, temporary rejections, and traps for impatient senders. How each defense works and how a good MTA passes them.
Building a Deliverability Monitoring Stack
Postmaster Tools, SNDS, FBLs, DMARC reports, TLS-RPT, bounce logs, engagement data: the full observability stack, what each layer catches, and the alerts worth paging on.
Duplicate Sends: Idempotency in Email Pipelines
Everyone has received the same email twice. The retry loops, queue semantics, and race conditions that cause duplicates, and the idempotency patterns that stop them.
Email Address Internationalization: SMTPUTF8 and EAI in Practice
Addresses like 佐藤@例え.jp are valid email. How EAI and SMTPUTF8 work, who supports them, and what sending systems break when a Unicode address shows up.
DNS for Email: The Records, TTLs, and Chains That Break Mail
Email is a DNS application. The full record inventory a sending domain needs, the TTL strategy for safe changes, and the misconfigurations that quietly break delivery.
Q4 Peak Sending: Ramping Volume Without Triggering Filters
Between Black Friday and year end, send volumes triple while filters tighten. How to ramp into peak season so November's volume looks like growth, not an incident.
DMARCbis: What Changes When DMARC Gets a New RFC
DMARCbis is finishing its journey through the IETF, replacing RFC 7489 with a Standards Track spec. The tree walk, retired tags, and what senders should do now.
SMTP Relay vs. API Sending: Architecture Trade-offs That Matter
Every sending platform offers SMTP relay and an HTTP API. The differences in latency, error handling, portability, and observability, and how to choose per workload.
Email Validation Services: What They Can and Cannot Do
Validation APIs verify syntax, domains, and mailbox existence. Where each check works, where catch-alls and traps defeat them, and where validation belongs in your stack.
Inbox Warmup Tools: Why Automated Engagement Backfires
Warmup services exchange automated opens and replies between member accounts to simulate engagement. Why providers treat this as manipulation and what to do instead.
Seed Testing and Inbox Placement: What the Numbers Really Measure
Seed lists promise a number for the question every sender asks: inbox or spam folder? What placement tests measure, where they systematically mislead, and how to use them.
SPF's 10-Lookup Limit: Includes, Flattening, and Permerror
Every include, a, mx, and redirect in your SPF record costs a DNS lookup, and the budget is ten. Why records break at scale and how to fix them without flattening regret.
Email Header Forensics: Reading Received Chains and Authentication-Results
Every delivery question has its answer in the headers. How to trace a message's path through Received lines and decode Authentication-Results like a postmaster.
Microsoft's New Outlook Sender Requirements: A Compliance Guide
Microsoft now requires SPF, DKIM, and DMARC from high-volume senders to Outlook consumer domains. What the rules demand, how enforcement works, and how to comply.
How AI-Generated Email Content Affects Deliverability
Spam filters do not detect AI authorship. They detect what careless AI usage produces: template sameness, volume spikes, and engagement decline. Where the real risks are.
NIS2 and Email Security: What EU Senders Need to Know
The NIS2 directive makes email authentication and transport security a regulatory matter for thousands of EU organizations. What it requires and where email fits.
Migrating ESPs Without Destroying Your Sender Reputation
Switching email providers resets your IPs, your DKIM keys, and every provider assumption about your traffic. A migration plan that carries your reputation across.
TLS-RPT: The Reporting Layer Your MTA-STS Deployment Is Missing
TLS-RPT delivers daily JSON reports on every failed TLS negotiation to your domain. The record, the report format, and how to turn failures into fixes.
MTA-STS in Practice: Adoption, Tooling, and Real Implementation
MTA-STS closes the STARTTLS downgrade hole by letting domains require verified TLS for inbound mail. The policy file, the DNS record, and the gotchas in between.
Parsing DMARC Aggregate Reports: From Raw XML to Decisions
RUA reports arrive as gzipped XML that nobody reads by hand. The report anatomy, a working parsing pipeline, and how to interpret the sources you will find.
Apple Mail Privacy Protection: What Open Rates Still Tell You
MPP fires your tracking pixel whether or not anyone reads the message. How the proxy works, how badly it skews your metrics, and what to measure instead.
DKIM Replay Attacks: How Spammers Weaponize Your Valid Signatures
A DKIM signature stays valid no matter who forwards the message. How replay attacks abuse that property to spend your reputation, and the defenses that limit the damage.
Spam Traps: Pristine, Recycled, and How Clean Senders Still Hit Them
Spam traps are addresses that never belonged on your list. The types, who operates them, how they end up in your database, and the hygiene that keeps them out.
Feedback Loops: Setting Up JMRP, Yahoo CFL, and a Complaint Data Pipeline
Feedback loops send you the complaints your recipients file. How to register with Microsoft, Yahoo, and the rest, and what to build so the data actually gets used.
Bounce Classification: Hard, Soft, and What Your Handling Logic Gets Wrong
Hard versus soft is not enough. How SMTP codes, enhanced status codes, and provider quirks should drive your retry, suppression, and reputation logic.
Engagement Signals Decoded: What Gmail's AI Actually Measures
Gmail's filtering models weigh replies, moves, stars, and deletes far more than the open rates senders obsess over. What the signals are and how to influence them.
The 0.3% Spam Complaint Threshold: How Postmaster Tools Actually Calculate It
Gmail enforces a 0.3% user-reported spam ceiling, but the denominator is inboxed mail, not sent volume. How the rate is computed and how to stay under it.
AMP for Email in 2024: Hype, Reality, and Whether to Bother
AMP for Email promised interactive inboxes. Six years after launch, here is who actually supports it, what it costs to run, and when the investment makes sense.
Postmaster Tools vs. SNDS: Reading Gmail and Microsoft Reputation Data
Gmail Postmaster Tools and Microsoft SNDS report sender reputation in fundamentally different ways. How to read both dashboards and act on what they actually show.
Deliverability Incident Response: A Playbook for the First 4 Hours
When email reputation collapses, the first 4 hours determine the recovery timeline. Triage, containment, communication the operational playbook teams actually need.
List Hygiene Beyond Bounces: Engagement-Based Suppression Strategies
Bounce-based list cleaning is decades behind modern deliverability. The 90/180/365-day engagement model, sunset policies, and re-engagement that actually works.
Blocklist Remediation Playbook: Spamhaus, SORBS, and UCEPROTECT
How to remove your IP or domain from Spamhaus, SORBS, UCEPROTECT, and other blocklists. Which lists matter, which to ignore, and the delisting process for each.
Sending from Subdomains: A Strategic Guide to Domain Architecture
How to architect email subdomains for reputation isolation. The 4-stream model, naming conventions, and why [send.brand.com] beats [mail.brand.com].
Why DMARC Alignment Matters More Than DMARC Itself
DMARC fails when SPF or DKIM pass for the wrong domain. The alignment rules, relaxed vs strict modes, and the ESP configuration that fixes it.
DKIM Key Rotation: A Practical Guide for Production Environments
How to rotate DKIM keys in production without breaking signatures. Dual-selector strategy, 2048-bit key sizes, and the rotation cadence that actually works.
One-Click Unsubscribe (RFC 8058): Implementation Pitfalls Most Senders Miss
RFC 8058 one-click unsubscribe is mandatory for bulk senders. The five implementation mistakes that fail compliance and how to test your endpoint properly.
Yahoo and Gmail's February 2024 Bulk Sender Requirements: A Compliance Checklist
The complete compliance checklist for Yahoo and Gmail's February 2024 bulk sender requirements. Authentication, unsubscribe, complaint rates—what you actually need.
The ARC Header: How Forwarding Breaks DMARC and What You Can Do
Forwarders break DMARC by modifying messages in transit. ARC (RFC 8617) preserves authentication results across hops. How it works, who supports it, and the limits.
BIMI Explained: Is the VMC Investment Worth It for B2B Senders?
BIMI displays your logo in supporting inboxes. The VMC certificate costs $1,500/year. Whether the brand recognition lift justifies the spend honestly assessed.
Why Your Transactional Emails Are Landing in Spam (And Mixing Them with Marketing Is The Reason)
Password resets going to spam? You're sending them from the same IP and domain as marketing campaigns. The four operational fixes that actually work.
IP Warming in 2023: A 30-Day Schedule That Actually Works
Most IP warming schedules fail because they ignore engagement segmentation. The 30-day ramp that actually works volume tables, segment ordering, and recovery rules.
The Hidden Cost of Shared IP Pools (And When to Move to Dedicated)
When to move from shared to dedicated IP pools. The volume threshold, reputation contamination risks, and the cost-benefit analysis ESPs don't want you to do.
Understanding DMARC Policies: From p=none to p=reject Without Breaking Things
How to move from DMARC p=none to p=reject without breaking production mail. The phased rollout that actually works with the failures most senders hit.
SPF Records Demystified: Why Your "v=spf1" Setup Is Probably Wrong
Most SPF records are subtly broken. The 10-lookup limit, multiple records, +all, and the alignment trap what's actually wrong with your SPF setup.