{
  stalwart-mail,
  callPackage,
  nixLib,
  rustPlatform,
  lib,
}: let
  spamfilter = callPackage ./spam-filter.nix {};
in
  stalwart-mail.override {
    rustPlatform =
      rustPlatform
      // {
        buildRustPackage = prev:
          rustPlatform.buildRustPackage (
            lib.attrsets.recursiveUpdate
            prev
            {
              pname = "stalwart-mail-patched";

              passthru = nixLib.warnMerge (prev.passthru or {}) {
                # Use a reproducible source for the spamfilter instead of fetching it at runtime from GitHub.
                inherit spamfilter;
              } "stalwart-mail passthru";

              cargoHash = "sha256-Rq18JumjKYt97WKIqnLakS+FQwsjt70irlYBYAYm3H8=";

              # The NixOS build tests should check if this works.
              # And this shaves of around 50% of the build time.
              doCheck = false;

              # We are already overriding it, so shaving of some unused features is okay.
              buildNoDefaultFeatures = true;
              buildFeatures = [
                # "sqlite"
                # "postgres"
                # "mysql"
                "rocks"
                # "elastic"
                # "s3"
                "redis"
                "tls-native-roots"
              ];

              cargoPatches =
                (prev.cargoPatches or [])
                ++ [
                  # `stalwart-mail` uses their bundled store, which makes it impossible to use our
                  # own CA certificate (e.g., for tests). Thus use a native version.
                  ./patches/0001-Allow-to-switch-to-operating-system-CA-root-store.patch
                ];

              # Check that the enterprise feature is really disabled.
              postCheck =
                (prev.postCheck or "")
                +
                # bash
                ''
                  if grep "enterprise" ./target/*/release/stalwart-mail.d; then
                    echo "ERROR: Proprietary 'enterprise' feature active."
                    exit 1
                  fi
                '';

              meta.mainProgram = prev.meta.mainProgram or "stalwart-mail";
            }
          );
      };
  }