anchor.diff:  
       substitute scripts/msmtpq/msmtp-queue $out/bin/msmtp-queue \
         --replace @msmtpq@ $out/bin/msmtpq
  +    ''}
  +    ${lib.optionalString preferNonBlock ''
  +    mkdir -p $out/lib/systemd/user
  +    cp ${nonblock}/msmtp* $out/bin/
  +    cp ${nonblock}/systemd/* $out/lib/systemd/user
  +    for f in $out/bin/msmtpq* ; do
  +      sed $f -i -r \
  +        -e 's|^QUEUE_DIR.*|QUEUE_DIR="''${MSMTP_QUEUE:-''${XDG_DATA_HOME:-$HOME/.local/share}/mail.queue}"|' \
  +        -e 's|^CONFIG.*|CONFIG="''${XDG_CONFIG_HOME:-$HOME/.config}/msmtprc"|' \
  +        -e 's| flock | ${eject}/bin/flock |'
  +    done
  +    for f in $out/lib/systemd/user/* ; do
  +      substituteInPlace $f \
  +        --replace /usr/local               $out \
  +        --replace .local/share/mail.queue  .cache/msmtp/queue
  +    done
  +    ''}
   
       chmod +x $out/bin/*
     '';
  
positive.code:   ];
  
    buildInputs = [ openssl gnutls gsasl libidn ]
      ++ stdenv.lib.optional stdenv.isDarwin Security;
    nativeBuildInputs = [ autoreconfHook pkgconfig ];
  
    configureFlags =
      stdenv.lib.optional stdenv.isDarwin [ "--with-macosx-keyring" ];
  
    postInstall = ''
      substitute scripts/msmtpq/msmtpq $out/bin/msmtpq \
        --replace @msmtp@      $out/bin/msmtp \
        --replace @nc@         ${netcat-gnu}/bin/nc \
  
negative.code: { stdenv, lib, fetchurl, fetchFromGitHub, autoreconfHook, pkgconfig
  , openssl, netcat-gnu, gnutls, gsasl, libidn, Security
  , systemd ? null, eject ? null }:
  
  let
    tester = "n"; # {x| |p|P|n|s}
    journal = if stdenv.isLinux then "y" else "n";
  
    # preferNonBlock = stdenv.isLinux;
    preferNonBlock = false;
  
    nonblock = fetchFromGitHub {
      owner  = "Stebalien";
      repo   = "msmtp-queue";
      rev    = "07032a4e4c8ea0d2364641c959db0c60f52423c7";
      sha256 = "0g2aph30007spkdwxljrlr2bliivf9nrdis3d3jvjpx8l6k60rr9";
    };
  
  in stdenv.mkDerivation rec {
    name = "msmtp-${version}";
  