rem: else if (column == mPaintInfo->subCol) return mSortSubject; else if (column == mPaintInfo->senderCol) {
add: else if (column == mPaintInfo->senderCol) return mSortSender; else if (column == mPaintInfo->subCol) {
context:   virtual QString key( int column, bool /*ascending*/ ) const {    if (column == mPaintInfo->dateCol) {      if (mPaintInfo->orderOfArrival)	return mSortArrival;      else	return mSortDate;    }    else if (column == mPaintInfo->subCol)      return mSortSubject;    else if (column == mPaintInfo->senderCol) {      if (mPaintInfo->status)	return QString( QChar( (char)mFolder->getMsgBase( mMsgId )->status() ));      else	return mSortSender;    }    else      return text(column);  }