Guías de autenticación de correo electrónico
Guías prácticas y directas sobre SPF, DKIM y DMARC. Corrija lo que está mal y mantenga su correo fuera del spam.
SMTP Error Codes Explained: 4xx and 5xx Bounces
A reference guide to SMTP reply codes and RFC 3463 enhanced status codes, covering the 2xx, 4xx, and 5xx classes, common bounces (421, 450, 451, 550, 552, 554), and how to act on each.
What Is the Return-Path (Envelope Sender)?
The Return-Path (envelope sender) is the hidden address SPF actually checks and where bounces are delivered. Learn how it differs from the visible From, why it controls SPF alignment for DMARC, and how a custom bounce domain fixes ESP traffic.
Email Deliverability Best Practices Checklist
A practical, checklist-driven guide to the seven pillars of email deliverability: authentication, infrastructure, warm-up, list hygiene, engagement, complaint and bounce thresholds, and monitoring.
What Is an MX Record and How Email Routing Works
A practical guide to MX records: what they contain, how priority values pick a receiving mail server, how MX differs from A and PTR records, and the common mistakes (CNAME targets, missing trailing dots) that break inbound email.
How to Read Email Headers to Check SPF, DKIM and DMARC
A practical walkthrough of email headers: how to open the raw source in Gmail, Outlook, and Apple Mail, then read the Received chain, Return-Path, and Authentication-Results to confirm SPF, DKIM, and DMARC or diagnose a failure.
What Is a PTR Record (Reverse DNS) for Email?
A PTR record is the reverse DNS entry that maps a sending IP back to a hostname, and mailbox providers now require a valid forward-confirmed match to accept mail. This guide explains FCrDNS, where PTR lives, and how to check and fix it.
What Is the List-Unsubscribe Header (One-Click Unsubscribe)?
A practical guide to the List-Unsubscribe and List-Unsubscribe-Post headers, RFC 8058 one-click unsubscribe, the 48-hour processing rule, and how to implement both headers correctly.
What Is ARC (Authenticated Received Chain)?
ARC preserves the original SPF, DKIM, and DMARC results when a message passes through a forwarder or mailing list. This guide explains the three ARC headers, how receivers validate the chain, and how ARC relates to DMARC.
2026 Bulk Email Sender Requirements: Google, Yahoo, Microsoft
The current 2026 checklist covering Gmail, Yahoo, Microsoft, and Apple bulk sender rules: SPF, DKIM, DMARC alignment, one-click unsubscribe, spam rate limits, and the enforcement timeline that now returns permanent rejections.
What Is Email Spoofing and How It Works
Email spoofing forges the visible From address by exploiting how plain SMTP separates the envelope from the message header. Learn how the forgery works, whether it is illegal, and how SPF, DKIM, and DMARC at p=reject actually stop it.
Should You Send Email From a Subdomain?
A practical guide to sending marketing and transactional email from dedicated subdomains: why reputation isolation protects your root domain, how it interacts with DMARC alignment and the sp= tag, and how to set it up.
What Is Email Authentication? A Complete Guide
A plain-language pillar guide to email authentication: why open SMTP has no built-in identity, and how SPF, DKIM, DMARC, and supporting signals like PTR, ARC, BIMI, and MTA-STS work together to prove a message really came from your domain.