mail2-nixos-config/nix/sources.json

{
    "nixos-mailserver": {
        "branch": "main",
        "repo": "https://codeberg.org/tokudan/nixos-mailserver.git",
        "rev": "0319598cd32793ef3c681c43e97848b8aadfa4df",
        "type": "git"
    }
}