Forward-Confirmed Reverse DNS (FCrDNS) Explained
FCrDNS adds an extra verification step beyond a basic PTR record, cross-checking that the forward and reverse DNS lookups for a sending IP actually agree with each other.
Google Postmaster Tools: A Technical Walkthrough
Google Postmaster Tools provides direct visibility into how Gmail specifically evaluates your sending domain, including reputation, spam rate, and authentication data unavailable anywhere else.
How Blocklists Work and How to Get Delisted
Blocklists (or blacklists) are third-party maintained databases of IPs and domains flagged for suspected spam or abuse, and understanding how listings happen — and how to resolve them — is a…
Implementing One-Click Unsubscribe (RFC 8058) Correctly
One-click unsubscribe is now a required technical feature for bulk marketing mail, and correctly implementing the underlying standard matters as much as simply having an unsubscribe link.
List-Unsubscribe and List-Unsubscribe-Post Headers Explained
These two specific headers work together to enable the one-click unsubscribe experience mail clients display, and both need to be correctly formatted for compliance.
Monitoring Domain Reputation With Microsoft SNDS
Microsoft's Smart Network Data Services provides IP-level reputation and complaint data specific to Outlook, Hotmail, and Live.com recipients, filling a gap that Google Postmaster Tools doesn't cover.
MTA-STS: Enforcing Transport Security for Inbound Mail
Mail Transfer Agent Strict Transport Security lets a domain explicitly require encrypted, authenticated connections for mail sent to it, closing a gap that opportunistic TLS alone leaves open.
TLS-RPT: Monitoring TLS Delivery Failures
TLS Reporting works alongside MTA-STS, giving domain owners visibility into TLS negotiation failures that would otherwise go completely unnoticed.
Understanding ARC (Authenticated Received Chain) for Forwarded Mail
ARC preserves authentication results as a message passes through intermediate systems, like mailing lists or forwarding services, solving a specific problem that DMARC alone creates for legitimately…
Understanding DMARCbis and What's Changed in the Updated Standard
DMARC has been formally elevated from an informational specification to a Proposed Standard, published as a set of RFCs that clarify and update several aspects of the original protocol.
Understanding Feedback Loops (FBLs) With ISPs
Feedback loops let major mailbox providers notify senders directly when a recipient marks their mail as spam, giving senders visibility they otherwise wouldn't have into real-time complaint behavior.
Understanding PTR Records and Reverse DNS
A PTR record maps a sending IP address back to a hostname, and its presence and consistency are checked by nearly every major receiving provider as a basic legitimacy signal.
Understanding the Google and Yahoo Bulk Sender Requirements
Any domain sending 5,000 or more messages per day to Gmail or Yahoo addresses is classified as a bulk sender and held to a specific, enforced set of technical requirements.
Understanding TLS in Email Transmission
Transport Layer Security encrypts the connection between mail servers during transmission, and its presence or absence is increasingly factored into deliverability decisions.
Using a Subdomain Strategy to Protect Your Root Domain
Sending marketing or transactional mail from a dedicated subdomain, rather than the root domain, isolates reputation risk and keeps unrelated business functions protected.
What Is IP Warming and Why It Still Matters
A new sending IP has no established reputation, and warming it up gradually is still a necessary technical practice for building the trust receiving providers require.
Building a Basic Deliverability Monitoring Checklist
A simple, consistent checklist applied on a regular cadence catches deliverability problems while they're still small and easy to fix.
Common DKIM Signing Mistakes That Break Alignment
DKIM can technically pass while still failing DMARC alignment, a subtle but common failure mode that trips up many senders relying on third-party email service providers.
DKIM Signing Explained: Keys, Selectors, and Headers
DKIM (DomainKeys Identified Mail) adds a cryptographic signature to outgoing messages, letting receiving servers verify the message wasn't altered in transit and genuinely originated from the claimed…
DMARC Explained: Policy, Alignment, and Reporting
DMARC (Domain-based Message Authentication, Reporting, and Conformance) ties SPF and DKIM together, adding a policy for how receiving servers should handle authentication failures and a reporting…