Articles and tutorials on communication infrastructure.
49–60 of 69 articles
A 4xx is not a failure, it is a negotiation. How to tell greylisting from reputation throttling, and the retry behaviour that recovers instead of escalating.
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.
Attackers use unprotected signup forms to bury a victim's inbox in confirmation mail. How the attack works, why your domain absorbs the damage, and how to close the door.
The links in your email resolve through a domain most senders never chose. Why shared tracking hosts get blocklisted and what a branded CNAME actually fixes.
How to architect email subdomains for reputation isolation. The 4-stream model, naming conventions, and why [send.brand.com] beats [mail.brand.com].
Every HTML email carries a second version almost nobody edits. How multipart nesting works, what breaks inside it, and why the text part still earns its place.
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.
How to rotate DKIM keys in production without breaking signatures. Dual-selector strategy, 2048-bit key sizes, and the rotation cadence that actually works.
RFC 8058 one-click unsubscribe is mandatory for bulk senders. The five implementation mistakes that fail compliance and how to test your endpoint properly.
The complete compliance checklist for Yahoo and Gmail's February 2024 bulk sender requirements. Authentication, unsubscribe, complaint rates—what you actually need.
Two regimes, two different questions. What CAN-SPAM requires at send time, what GDPR requires before it, and the consent record that survives a complaint.
IP reputation can be rented and replaced. Domain reputation cannot. How providers weight the two, what survives a migration, and where reputation spending is misallocated.