- Renamed `setting.main` to `settings.main` in the Postfix module for consistency with configuration standards.
- Ensured proper functionality of service by aligning with expected key structure.
- Renamed and reorganized configuration keys for consistency (`settings` usage).
- Updated Postfix, systemd, and Syncthing configurations to adhere to the standardized format.
- Improved maintainability and readability of NixOS configurations.
Adjusted the virtual_alias_maps to properly include both root and admin email forwarding. Removed unused rootAlias line and ensured the configuration aligns with intended email routing behavior.
Added configuration for Postfix to use an external SMTP relay with encrypted credentials managed by SOPS. Updated `mail.nix` to include relay settings and linked the secrets file for password storage.
Introduce `mail.nix` to configure mail utilities (`mailutils`, `mutt`) and enable Postfix service. Updated `default.nix` to include the new configuration file.
