·Deliverability
Gmail promotions tab, 2026: what actually moved the needle
Six months of controlled tests across four verticals. What still helps, what stopped mattering, and what to stop worrying about.
Full text available on request — contact.
Resources
Blog
Working notes from the engineering team. We publish when there is something worth saying, and archive rather than delete. Individual posts are available on request during engagements.
·PowerMTA
Notes on PowerMTA 5.2 in production
Three months in. Notable behavioural changes, config migration gotchas, and the one accounting-log field we now depend on.
Full text available on request — contact.
·Authentication
ARC in the wild, three years on
Where ARC actually helps recover DMARC alignment across forwarders, and where receivers still ignore it.
Full text available on request — contact.
·Operations
Runbooks over dashboards
Why our on-call still opens a markdown file before any web UI.
Full text available on request — contact.
·Infrastructure
Retiring an IPv4 /24: an obituary and a lessons-learned
The pool served us since 2014. Here is the reputation curve, and what we did on the transition.
Full text available on request — contact.
·Deliverability
Outlook Focused inbox: what we can and cannot see
SNDS shows one thing, seed panels show another. How we reconcile the two.
Full text available on request — contact.
·DMARC
A quiet fix for aggregate report ingestion at scale
How we cut our aggregate-report ingestion pipeline latency by an order of magnitude. Not glamorous, but useful.
Full text available on request — contact.
·Warm-up
The wrong first-day segment kills more warm-ups than volume does
Data from 48 warm-ups over 18 months. First-day audience quality dominates.
Full text available on request — contact.
·Bounces
Reading Yahoo's TS-codes correctly
The most under-utilised diagnostic signal in high-volume sending.
Full text available on request — contact.
·Security
Rotating DKIM without downtime, actually
The step everyone gets wrong is TTLs. Here is the sequence we run every six months.
Full text available on request — contact.
·Deliverability
Google Postmaster 'no data': the four causes
Not always volume. A short diagnostic tree.
Full text available on request — contact.
·Infrastructure
Cross-region MTA failover: what we actually do
Not automatic. Not always desirable. Here is our current playbook.
Full text available on request — contact.
·Operations
Year-end review 2025
What we shipped, what we broke, what we learned.
Full text available on request — contact.
·Deliverability
The complaint-rate cliff at Microsoft
Below 0.1% is fine. Above 0.3% is catastrophic. The transition is faster than most senders think.
Full text available on request — contact.
·BIMI
BIMI in 2025: is the VMC still worth it?
For the third year running, still yes — for the right brands. Numbers included.
Full text available on request — contact.
·Postfix
Postfix at 100M/month: what we would change
Notes from six months operating a Postfix deployment at volumes usually associated with PowerMTA.
Full text available on request — contact.
·Deliverability
Segmentation is deliverability
The single largest variable most senders can still control.
Full text available on request — contact.
·Authentication
SPF flattening: still useful, still fragile
How to do it, when to avoid it, and how to keep it maintained.
Full text available on request — contact.
·Compliance
Reading the Gmail & Yahoo 2024 sender requirements two years later
What actually got enforced, what quietly did not, and what to still take seriously.
Full text available on request — contact.
·Operations
Incident report: a strange Comcast defer pattern
How we diagnosed and remediated a pattern that only affected one third of traffic.
Full text available on request — contact.
·Deliverability
Why 'engagement' does not mean what your ESP dashboard says it means
Provider-side engagement and platform-side engagement are not the same signal.
Full text available on request — contact.
·PowerMTA
VMTA topology for multi-brand programmes
The mistake we see most: too few VMTAs, too broad a policy.
Full text available on request — contact.
·Infrastructure
On not chasing new dependencies
A note on why our stack does not change much year to year.
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·DMARC
The p=quarantine trap
Why some senders sit in quarantine forever, and how to get them out.
Full text available on request — contact.
·Bounces
Suppression is not a warehouse: it is infrastructure
How to think about suppression as an enforced constraint, not a list.
Full text available on request — contact.
·Deliverability
Seed panels are directional, not decisive
The right way to weight seed data against Postmaster and SNDS.
Full text available on request — contact.
·Operations
Change control for sending configuration
The lightweight process we ask every client to adopt after their second self-inflicted incident.
Full text available on request — contact.
·Warm-up
Warm-up curves for programmes above 10M/day
Volumes at which the standard curves stop working and what replaces them.
Full text available on request — contact.
·Deliverability
The Gmail feedback loop that isn't
How to synthesise the complaint signal Gmail refuses to expose.
Full text available on request — contact.
·Infrastructure
IPv6 outbound: the state in 2025
What has changed, what has not, and where we currently draw the line.
Full text available on request — contact.