SELECT start, from_number FROM mango
UNION
SELECT DateE, Message FROM email

SELECT
  start, from_number, DateE, Message
FROM
  mango
  LEFT JOIN email ON mango.from_number != email.Message

select distinct x1,x2,x3
    from
    (
     SELECT start as x1 , from_number as x2, 1 as x3 FROM mango
      UNION
     SELECT DateE, Message, 2 FROM email
    ) as t