SQL & PL/SQL

hw to use function below--

FUNCTION vrfy(c IN OUT NOCOPY connection,
recipient IN VARCHAR2) RETURN reply;

i want to check if senders address i m sending is right or not means exists on server or not

sample code---
declare
vs_errordesc varchar2(4000);
vs_conn UTL_SMTP.connection;
reply varchar2(1000);
begin
vs_conn := UTL_SMTP.open_connection (xyz.com',25);
UTL_SMTP.helo (vs_conn,'xyz.com');

UTL_SMTP.VRFY (vs_conn,'abc@xyz.com') ;

dbms_output.put_line (reply);

exception when others then
vs_errordesc :=sqlerrm;
dbms_output.put_line (vs_errordesc);
end;

i want to check whts reply hw can i check it?

i m getting error here
--UTL_SMTP.VRFY (vs_conn,'abc@xyz.com') ;
can u anyone help