Gmail verifies the sender, not the desire to receive those emails
Gmail's program for U.S. political committees does not promise the inbox. It formalizes a known rule: identity opens the door, reputation decides what follows.
DKIM
DomainKeys Identified Mail setup, key rotation, and troubleshooting.
29 articles
August 2026
June 2026
Hornetsecurity Secure Email Gateway (ex-Vade): architecture, DNS configuration and alternatives
Hornetsecurity 365 Total Protection is the cloud SEG for SMBs and MSPs (ex-Vade, now Proofpoint). Complete guide: architecture, mx01.hornetsecurity.com MX, spf.hornetsecurity.com SPF include, DKIM by CNAME, gateway vs API and a comparison with Proofpoint/Barracuda/Mimecast.
Barracuda Email Gateway Defense: architecture, DNS configuration and alternatives
Barracuda Email Gateway Defense is the cloud SEG for SMBs and MSPs (200,000+ customers). Complete guide: architecture, *.ess.barracudanetworks.com MX, SPF/DKIM/DMARC, DNS detection, the distinction with the ESG appliance (CVE-2023-2868) and a comparison with Mimecast/Proofpoint/Defender.
ARC moves to "Historic" status at the IETF: should you still care in 2026?
The IETF is reclassifying ARC (RFC 8617) as "Historic." But deprecated on paper does not mean dead in practice: Apple, Google and Microsoft still require it. Here is what really changes and what you should do.
May 2026
April 2026
Cloudflare Email Service: Email Routing, Security, and DMARC Management explained
Cloudflare now covers 4 email layers: free Email Routing, transactional Email Service (public beta April 2026), anti-phishing Email Security (formerly Area 1), and DMARC Management. Complete guide covering architecture, DNS, Proofpoint/Mimecast comparison, and pricing.
Cisco Secure Email Cloud Gateway (CES): SaaS architecture, iphmx.com DNS and ESA migration
Cisco Secure Email Cloud Gateway (CES) is Cisco's primary SaaS offering in 2026, the successor to the legacy ESA appliances inherited from Ironport. Complete guide: CES onboarding, iphmx.com MX records by region (NA/EU/APJ), SPF/DKIM/DMARC, migration from ESA to CES, 2024-2025 Gartner Magic Quadrant exit, zero-day CVE-2025-20393, comparison with Proofpoint, Mimecast, Defender and Abnormal.
Abnormal Security: behavioral AI, API deployment, and email gateway alternatives
Abnormal Security is an API-native ICES platform that detects BEC, VEC, and Account Takeover attacks using behavioral AI, with no MX change required. Complete guide: Attune 1.0 architecture, Proofpoint/Mimecast/Defender comparison, limitations, and DNS record audit.
Proofpoint Secure Email Gateway: architecture, DNS configuration and alternatives
Proofpoint is the enterprise SEG benchmark, used by 87 of the Fortune 100. Complete guide: Nexus AI architecture, TAP, SPF/DKIM/DMARC configuration, the 2024 EchoSpoofing incident and a comparison with Mimecast, Microsoft Defender and Abnormal Security.
Mimecast Secure Email Gateway: how it works, DNS setup, and alternatives
Mimecast is a cloud email gateway (SEG) that intercepts all traffic via MX redirection. Full guide: architecture, SPF/DKIM/DMARC setup, Proofpoint/Abnormal Security comparison, and DNS audit.
March 2026
Test Email Deliverability: The Complete Guide Before Sending
One in five emails never reaches the inbox. This guide shows you how to test your email deliverability before sending and fix every issue.
February 2026
January 2026
Postmark (ActiveCampaign): Complete Technical Guide to Transactional Email
Detailed technical guide for developers: DNS configuration (DKIM, custom Return-Path), REST API vs SMTP, Message Streams, dedicated IP, webhooks and 2026 pricing.
Mandrill (Mailchimp Transactional): Technical Guide for Transactional Email
A complete guide for developers and system admins: DKIM configuration via CNAME, choosing between API and SMTP, Mailchimp prerequisites, and pitfalls to avoid.
Mailgun: Complete Technical Guide for Transactional Email
A detailed technical guide for developers: DNS configuration (SPF, 2048-bit DKIM with autorotation), REST API vs SMTP, dedicated vs shared IP, limits and webhooks.
Amazon SES: Complete Guide to DNS Configuration and Email Authentication
Complete Amazon SES configuration with Easy DKIM, Custom MAIL FROM, strict DMARC alignment. Everything you need for optimal deliverability and GDPR compliance.
Mailjet: Complete Technical Guide for Transactional Email in 2026
A comprehensive guide for developers and system admins: DKIM configuration, API v3 vs v3.1, dedicated vs shared IP, and pitfalls to avoid with Mailjet.
Twilio SendGrid: Complete Technical Guide for Transactional Email
A detailed technical guide for developers: DNS configuration (SPF, 2048-bit DKIM), Web API v3, SMTP Relay, dedicated vs shared IP, limits and webhooks.
Brevo (formerly Sendinblue): Technical Guide for Transactional Emailing
A comprehensive guide for developers and sysadmins: DKIM configuration, choosing between API and SMTP, technical limits, and pitfalls to avoid with Brevo.
December 2025
Connect CaptainDNS to ChatGPT via MCP: 3 widgets for DNS audits and deliverability
Add the CaptainDNS MCP server to ChatGPT and use 3 widgets to troubleshoot DMARC/DNS and analyze email headers without leaving the conversation.
November 2025
October 2025
