anchor.diff:        type = types.nullOr types.str;
         default = null;
         description = "Default group to store mail for virtual users.";
  +    };
  +
  +    createMailUser = mkOption {
  +      type = types.bool;
  +      default = true;
  +      description = ''Whether to automatically create the user
  +        given in <option>services.dovecot.user</option> and the group
  +        given in <option>services.dovecot.group</option>.'';
       };
   
       modules = mkOption {
  
positive.code:     paths = map (pkg: "${pkg}/lib/dovecot") ([ dovecotPkg ] ++ map (module: module.override { dovecot = dovecotPkg; }) cfg.modules);
    };
  
  in
  {
  
  
negative.code: 
      enablePop3 = mkOption {
        type = types.bool;
        default = false;
        description = "Start the POP3 listener (when Dovecot is enabled).";
      };
  
  