anchor.diff:      ++ stdenv.lib.optional enableLDAP openldap
       ++ stdenv.lib.optionals enableMySQL [ mysql.connector-c zlib ]
       ++ stdenv.lib.optional enableAuthDovecot dovecot
  -    ++ stdenv.lib.optional enablePAM pam;
  +    ++ stdenv.lib.optional enablePAM pam
  +    ++ stdenv.lib.optional enableSPF libspf2;
   
     preBuild = ''
       sed '
  
positive.code:         s:^\(EXTRALIBS_EXIM\)=\(.*\):\1=\2 -lpam:
          s:^# \(EXTRALIBS_EXIM\)=.*:\1=-lpam:
        ''}
        #/^\s*#.*/d
        #/^\s*$/d
      ' < src/EDITME > Local/Makefile
  
negative.code: , enableMySQL ? false, mysql, zlib
  , enableAuthDovecot ? false, dovecot
  , enablePAM ? false, pam
  , enableSPF ? true, libspf2
  }:
  
  stdenv.mkDerivation rec {
  