The problem seems to be a missing "*" metacharacter. I've put a small test case together:
WITH t AS (SELECT 'Test@oracle.com' email
FROM dual
UNION
SELECT '1@oracle.com'
FROM dual
)
SELECT t.email
, REGEXP_SUBSTR(t.email, '^([0-9a-zA-Z]([-.\w]*[0-9a-zA-Z])*@([0-9a-zA-Z][-\w]*[0-9a-zA-Z]\.)+[a-zA-Z]{2,9})$') orig_check
, REGEXP_SUBSTR(t.email, '^([0-9a-zA-Z]([-.\w]*[0-9a-zA-Z])*@([0-9a-zA-Z]*[-\w]*[0-9a-zA-Z]\.)+[a-zA-Z]{2,9})$') new_check
FROM t
;
I'm going to deal with inet specific values (IP4 addresses, emails, URLs) in the second part of my regex introduction.
C.
