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Cover Image for RCPT TO and Invalid Recipients: How Attackers Enumerate Email Addresses over SMTP

Jul 9, 2026·7 min·E-Mail-Sicherheit / Technik

RCPT TO and Invalid Recipients: How Attackers Enumerate Email Addresses over SMTP

A 250 or 550 response to RCPT TO can quietly reveal whether an email address exists. This guide explains how SMTP recipient enumeration works at the protocol level, how it feeds a directory harvest…

Cover Image for MTA-STS vs DANE: Which TLS Standard Protects Email Transport Better?

Jul 2, 2026·8 min·E-Mail-Sicherheit / Vergleich

MTA-STS vs DANE: Which TLS Standard Protects Email Transport Better?

MTA-STS and DANE both make TLS mandatory for email transport, yet they secure the connection in fundamentally different ways. This guide compares trust anchors, the DNSSEC requirement, trust on first…

Cover Image for How to Set Up MTA-STS for Microsoft 365: Step-by-Step

Jun 30, 2026·7 min·E-Mail-Sicherheit / Anleitung

How to Set Up MTA-STS for Microsoft 365: Step-by-Step

A concrete walkthrough for enabling MTA-STS on Microsoft 365 and Exchange Online. Learn why EXO cannot serve the policy file, which DNS records and subdomain you need, how to list the…

Cover Image for What Is DANE? Certificate Binding Through DNSSEC Explained

Jun 27, 2026·6 min·Email Security / Fundamentals

What Is DANE? Certificate Binding Through DNSSEC Explained

DANE anchors a mail server TLS certificate in DNS through DNSSEC and protects against downgrade and certificate spoofing. This guide explains what DANE and TLSA are, how certificate binding works,…

Cover Image for What Is a Directory Harvest Attack (DHA)? Explained

Jun 27, 2026·6 min·Email Security / Fundamentals

What Is a Directory Harvest Attack (DHA)? Explained

A directory harvest attack, DHA for short, collects valid email addresses over SMTP for later spam and phishing waves. This guide explains what a directory attack is, how it differs from address…

Cover Image for What Is MTA-STS? How It Works and How to Set It Up

Jun 27, 2026·5 min·Email Security / Fundamentals

What Is MTA-STS? How It Works and How to Set It Up

MTA-STS makes TLS mandatory for email transport and protects against downgrade attacks. This guide explains what MTA-STS is, how the policy works technically, how it differs from STARTTLS and DANE,…

Cover Image for Securing Postfix: Best Practices, main.cf Snippets & Architecture Tips

Jun 24, 2026·4 min·Linux

Securing Postfix: Best Practices, main.cf Snippets & Architecture Tips

How to secure your Postfix mail server: Practical main.cf configuration snippets, Postscreen setup, RBLs, and the architectural shift to a Secure Email Gateway.

Cover Image for Outlook Signature Disappears? 6 Common Problems + Easy Fixes

May 14, 2026·10 min·Tips & Troubleshooting / IT Administration

Outlook Signature Disappears? 6 Common Problems + Easy Fixes

You create your Outlook signature – and the next day it's gone. The signature isn't showing, after an update all settings are lost, or the native Outlook feature completely breaks down. Sound…

Cover Image for Conbool Disclaimer Add‑in for Outlook – Now in the Microsoft Store

May 10, 2026·8 min·Product Updates / News

Conbool Disclaimer Add‑in for Outlook – Now in the Microsoft Store

Centrally control email signatures, add legally compliant disclaimers, and unify your company's brand in Outlook – without manual hassle. The Conbool Disclaimer Add‑in is now officially available in…

Cover Image for SecureMail: Email Encryption Without Plugin Chaos and Portal Frustration

Apr 25, 2026·3 min·IT Security / Mail Encryption

SecureMail: Email Encryption Without Plugin Chaos and Portal Frustration

Forget complicated portals and HTML attachments. Learn how to encrypt emails adaptively and GDPR-compliant in Microsoft 365 with Conbool SecureMail.

Cover Image for Email Security Gateway: The Complete Guide for Businesses 2026

Mar 29, 2026·5 min·IT Security / Email

Email Security Gateway: The Complete Guide for Businesses 2026

An Email Security Gateway is the central line of defense for business email communication. This guide explains how it works, what threats it blocks, and why it is essential for NIS2 and GDPR…

Cover Image for Email Security Gateway Comparison 2026: What Really Matters

Mar 29, 2026·3 min·IT Security / Comparison

Email Security Gateway Comparison 2026: What Really Matters

Choosing the right Email Security Gateway is critical for business communication security. This comparison shows the most important criteria and typical pitfalls.