Blog

Technische Einblicke in E-Mail-Zustellbarkeit, Infrastruktur-Härtung und datenschutzorientiertes Design.

März 29, 2026
The Email Deliverability Landscape in 2026
Google, Yahoo, and Microsoft now require SPF, DKIM, and DMARC for all commercial senders. Here's what changed and what it means for your infrastructure.
deliverability authentication DMARC
März 14, 2026
Postfix TLS: Beyond Opportunistic Encryption
Most mail servers support TLS but don't enforce it. DANE, MTA-STS, and proper protocol configuration close the gap between "encrypted sometimes" and "encrypted always.
TLS DANE MTA-STS Postfix
Februar 27, 2026
SPF, DKIM, DMARC, and ARC: The Complete Authentication Stack
Email authentication is no longer optional. Here's how the four protocols work together — and why ARC is critical for anyone who forwards mail.
SPF DKIM DMARC ARC authentication
Februar 12, 2026
SRS: Why Forwarded Email Breaks SPF and How to Fix It
When you forward an email, SPF fails. The Sender Rewriting Scheme fixes this — and without it, forwarded mail from strict domains gets rejected.
SRS SPF forwarding Postfix
Januar 28, 2026
Spam Filtering Architecture: Milters, Bayes, and Greylisting
Authentication proves mail is legitimate. Spam filtering proves it isn't malicious. Here's how to architect a filtering stack that protects deliverability.
spam Rspamd Bayes greylisting milter
Januar 10, 2026
Rate Limiting and Abuse Prevention for Mail Servers
Connection floods, brute-force attacks, and spam bursts all hit the SMTP port. Here's how to stop them at multiple layers without blocking legitimate mail.
rate limiting abuse prevention Postfix Fail2ban
Dezember 27, 2025
DNS Security for Email: DNSSEC, DANE, and Local Resolvers
DNS is the foundation of email authentication. If your DNS can be spoofed, SPF, DKIM, and DMARC are all meaningless. Here's how to secure it.
DNS DNSSEC DANE Unbound
Dezember 10, 2025
Monitoring Your Mail Stack: Proving It Works
A correctly configured mail server that silently stops processing mail is worse than a misconfigured one. Here's how to monitor every layer and catch failures before users do.
monitoring Monit operations deliverability