- Upgrade NixOS channel from 25.05 to 25.11 - Fix dovecot systemd service rename (dovecot2 -> dovecot) - Convert postfix numeric settings to integers (25.11 requirement) - Remove insecure 512-bit DH params, fix 2048-bit DH params - Update postfix ciphers to modern ECDHE/DHE+AESGCM/CHACHA20 - Require TLS 1.2 minimum for OpenLDAP - Remove weak ciphers (3DES, RC4, aNULL) from OpenLDAP