wht do u actually want???
can u give us some example?

(eg) [email protected] fro this do u want abc alone or xyz.com

"abc"
select substr('[email protected]', 1, instr('[email protected]', '@') -1 ) from dual;

"xyz.com"
select substr('[email protected]', instr('[email protected]', '@') +1 ) from dual;


Cheers!