Email deliverability
SPF, DKIM, DMARC, sender reputation, newsletters, consent and bounces.
BIMI: showing your brand logo in the inbox
What BIMI is, which DMARC requirements it imposes, how to prepare the SVG logo, what VMC and CMC certificates are for and what to really expect from providers.
Bulk sender requirements: what Gmail and Yahoo demand
The rules Gmail and Yahoo introduced for high-volume senders: authentication, DMARC, one-click unsubscribe, spam rate and how to check each of them.
DKIM: selectors, key length and rotation without downtime
How DKIM selectors work, which key length to choose, how to publish the DNS record and how to rotate keys without losing messages along the way.
DMARC aggregate reports: how to read them and what to look for
The structure of DMARC rua reports in XML, how to interpret records, results and alignment, and how to tell legitimate sources from spoofing attempts.
DMARC alignment: From, Return-Path and DKIM signature compared
Why a message can pass SPF and DKIM yet fail DMARC: the three domains in an email, relaxed and strict alignment, and how to choose between the two.
DMARC from p=none to p=reject: a gradual, safe path
The stages for moving a DMARC policy from monitoring to rejection: source inventory, progressive quarantine, subdomains and checks after the switch.
DNSBL blocklists: how to check them and really get delisted
How DNS-based blocklists for IPs and domains work, which ones actually matter, how to verify a listing and how to get removed without being listed again.
Double opt-in: collecting real subscribers and provable consent
How double opt-in works, why it improves list quality and delivery, how to write the confirmation email and which data to keep as evidence of consent.
Email content and HTML: what spam filters really look at
How much content matters for delivery: linked domains, clean HTML, plain-text part, images, URL shorteners and the myth of forbidden words in subjects.
Email forwarding, SRS and ARC: why authentication breaks
What happens to SPF, DKIM and DMARC when a message is forwarded or goes through a mailing list, and how SRS and ARC help you avoid losing legitimate mail.
Feedback loops and spam complaints: receiving reports and acting
How provider feedback loops work, the ARF format, the Feedback-ID header, and how to use spam complaints to unsubscribe people and fix the causes.
Hard bounces and soft bounces: reading and handling them well
What separates hard and soft bounces, how to read SMTP codes and error text, when to suppress an address and when to retry, with a clear policy.
Inactive subscribers: re-engagement campaigns and sunset policy
How to define an inactive subscriber when opens are unreliable, how to run a re-engagement campaign and set a sunset policy that protects deliverability.
Sender reputation: IP address and domain compared
How providers assess IP and domain reputation, the difference between shared and dedicated IPs, and which behaviours build reputation or damage it over time.
List-Unsubscribe and one-click unsubscribe: doing it right
How to implement the List-Unsubscribe and List-Unsubscribe-Post headers: POST endpoint, signed tokens, DKIM coverage and proper handling of requests.
MTA-STS and TLS-RPT: enforcing encryption on inbound mail
Why STARTTLS alone is not enough, how to publish an MTA-STS policy in testing and enforce modes, and how to read TLS-RPT reports on encryption failures.
Postmaster Tools and SNDS: monitoring reputation at providers
How to set up and read the sender tools from Gmail and Microsoft: spam rate, authentication, IP status, and how to turn the data into concrete actions.
Testing deliverability before you send: seed inboxes and checks
A practical procedure for checking a send before it goes out: authentication headers, test mailboxes, placement tests, links and the plain-text version.
PTR, reverse DNS and HELO: requirements for your own mail server
What receivers check on a self-managed mail server: PTR record, forward and reverse match, HELO name, TLS and IP addresses suitable for direct sending.
Sender name, From and Reply-To: choosing a recognisable identity
How to choose display name, From address and Reply-To, why no-reply addresses are a mistake and how to keep a consistent identity over time.
Signup forms and bots: stopping fake sign-ups and list bombing
How bots abuse signup forms to flood other people's inboxes, the damage they do to your reputation and the defences to use: honeypots, limits, opt-in.
Spam traps: what they are, how they get in and how to avoid them
Pristine, recycled and typo spam traps: how they work, why they also hit honest senders, and which collection and hygiene practices keep them out.
SPF and the 10 DNS lookup limit: diagnosis and fixes
Why an SPF record with too many includes fails with permerror, how to count DNS lookups and how to reduce them without breaking third-party senders.
Transactional email: reliable receipts, resets and notifications
How to get order confirmations, codes and password resets delivered on time: separation from campaigns, app-side sending, queues, retries, monitoring.
Warming up a new IP or domain: a step-by-step plan
Why an IP or domain with no history must be warmed up, how to build a volume ramp, which segments to send to first and which signals tell you to slow down.