Hardening Postfix TLS to Pass Internet.nl in 2026

On April 21, 2026, Internet.nl rolled out a fully updated TLS test based on the latest NCSC-NL guidelines. Mail servers that previously passed the test may now show new warnings. This guide walks through the exact fixes on Debian 13 Trixie with Postfix 3.9 or later, based on hands-on troubleshooting on a production server. The...