File Attachment Size

I hace an Execute SQL task which calls a  sproc which contains the  sp_send_mail  system sproc to e-mail a set of query results . It is OK as long as the query results are small, but I get this error if they get too big: - File attachment or query results size exceeds allowable value of 1000000 bytes.

any way to change (and where to change) this value.

Dave