Articles & Guides
Useful resources for web developers and system administrators
Infrastructure
Warming Up a Sending Domain
Warm up a sending domain and IP for email: a day-by-day volume schedule, gradual ramp, starting with your most engaged subscribers, and reputation monitoring.
Infrastructure
Transactional Email Deliverability
How to make transactional email land: a dedicated subdomain, SPF/DKIM/DMARC, stream separation, and MX/SMTP monitoring — practical, battle-tested rules.
Infrastructure
Why Emails Bounce: Codes and Causes
Why emails bounce: SMTP 5xx and 4xx codes explained, the real causes — bad address, reputation block, SPF/DKIM/DMARC failure — and how to fix each one.
Infrastructure
Email Bounce Handling: Hard vs Soft
How to handle email bounces: the hard vs soft difference, SMTP 4xx and 5xx codes, suppression-list rules and automation to protect your sender reputation.
Security
BIMI Setup Guide: Brand Logo in Email
BIMI shows your brand logo next to email. How to set it up: SVG Tiny PS logo, a VMC certificate, the default._bimi TXT record and required DMARC enforcement.
Security
Migrating DMARC to p=reject Safely
Migrate DMARC from p=none to quarantine and reject without losing legitimate email: a staged pct rollout, reading RUA reports, and monitoring with enterno.io.
Security
Reading DMARC Aggregate (RUA) Reports
Reading DMARC RUA reports: how to parse XML aggregates, source IP, SPF and DKIM results, alignment and disposition. Move from p=none to p=reject safely.
Security
Email Spoofing Prevention
Email spoofing prevention: how spoofing works and how to stop it with SPF, DKIM and DMARC together. Real records, dig verification and the p=reject policy.
Security
DKIM Setup Guide: Key, Selector, DNS
DKIM setup step by step: generate the key, pick a selector, publish the TXT record in DNS and verify it with dig. Example records and common DKIM mistakes.
DNS
SPF Too Many DNS Lookups (10-Lookup Limit) Fix
SPF too many DNS lookups error: what the 10-lookup limit means and how to fix it. Counting include, mx, a, SPF flattening, macros and checking with dig.