code: @Override
      public boolean searchShouldStop(Search<?> search) {
          return search.getMinDelta() != JamesConstants.INVALID_DELTA && search.getMinDelta() < minDelta;
      }
docs: Checks whether the minimum delta observed during the current run of the given
  search is still above the required minimum.
  
  @param search search for which the minimum delta has to be checked
  @return <code>true</code> in case of a minimum delta below the required minimum