rem: return mSortSender;
add: return text(mPaintInfo->senderCol).lower() + " " + mSortArrival;
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->senderCol)      return mSortSender;    else if (column == mPaintInfo->subCol) {      if (mPaintInfo->status)	return QString( QChar( (char)mFolder->getMsgBase( mMsgId )->status() ));      else	return mSortSubject;    }    else      return text(column);  }