SELECT name, email FROM clients WHERE DATE_FORMAT(lastsend, '%d/%m/%y') <> DATE_FORMAT(now(), '%d/%m/%y')

UPDATE clients SET lastsend = Now();

WHERE DATE_FORMAT(lastsend, '%d/%m/%y') <> DATE_FORMAT(now(), '%d/%m/%y') and
      DATE_FORMAT(sendstart, '%d/%m/%y') <> DATE_FORMAT(now(), '%d/%m/%y')