SQL & PL/SQL :: Fail While Validating Email ID

I am creating function for validating email id :

create or replace function f_is_valid_email(p_email in varchar2) return varchar2 is

begin
if REGEXP_LIKE(p_email, '^[a-zA-Z0-9._%-]+@[a-zA-Z0-9._%-]+.{1}[a-zA-Z]$') then
return 'success';
ELSE
RETURN 'Failure' ;
END IF;
end f_is_valid_email;

But this function fail when

i did
SELECT f_is_valid_email('aaa..ss@AA.com') from dual
or
SELECT f_is_valid_email('aaa.ss@AA..com') from dual