anchor.diff:            ln -sf ${virtualFile} /var/postfix/conf/virtual
             ln -sf ${mainCfFile} /var/postfix/conf/main.cf
             ln -sf ${masterCfFile} /var/postfix/conf/master.cf
  +          ln -sf ${transportFile} /var/postfix/conf/transport
   
             ${pkgs.postfix}/sbin/postalias -c /var/postfix/conf /var/postfix/conf/aliases
             ${pkgs.postfix}/sbin/postmap -c /var/postfix/conf /var/postfix/conf/virtual
  
positive.code:   virtualFile = pkgs.writeText "postfix-virtual" cfg.virtual;
    mainCfFile = pkgs.writeText "postfix-main.cf" mainCf;
    masterCfFile = pkgs.writeText "postfix-master.cf" masterCf;
  
  in
  
  
negative.code:         default = "";
          description = "
            Entries for the virtual alias map, cf. man-page virtual(8).
          ";
        };
  
        transport = mkOption {
          default = "";
          description = "
            Entries for the transport map, cf. man-page transport(8).
          ";
        };
  
  