EXISTS vs. IN - EXISTS does not work by IN does

Question

I have a query with 3 subqueries. Values must be in all three subqueries to be returned. My test case is commented out in the query below. When I use the subquery using an in statement /* in the commented section */ the test case does not get returned and it SHOULD NOT be returned. IN works. When I use the EXISTS subquery, it does get returned and it SHOULD NOT be returned.
Am I not using EXISTS correctly?
/* Formatted on 2006/07/21 11:14 (Formatter Plus v4.8.5) */
SELECT DISTINCT sa.email
FROM salesagent sa, security s
WHERE sa.vendor_id IN (SELECT vendor_id
FROM vendor_fed_classifications
WHERE vendor_type_id = 1)
AND sa.salesagent_id IN (SELECT salesagent_id
FROM salesagent_verticals
WHERE subcategory_id = 158)
AND sa.email_enabled = 1
AND s.user_id = sa.salesagent_id
AND s.security_status = 'Reg'
--AND sa.email = '[email protected]'
/* AND sa.salesagent_id IN (
SELECT salesagent_id
FROM salesagent_agency
WHERE agency_id =
(SELECT agency_id
FROM customer
WHERE customer_id = (SELECT owner_id
FROM auction2
WHERE auction_id = 29465)))
AND EXISTS (
SELECT salesagent_id
FROM salesagent_agency
WHERE agency_id =
(SELECT agency_id
FROM customer
WHERE customer_id = (SELECT owner_id
FROM auction2
WHERE auction_id = 29465)))
ORDER BY 1;

Answer 1

You'll also probably want to simplify either of those subqueries a bit.
SELECT DISTINCT sa.email
  FROM salesagent sa, security s
WHERE sa.vendor_id IN (SELECT vendor_id
                          FROM vendor_fed_classifications
                         WHERE vendor_type_id = 1)
   AND sa.salesagent_id IN (SELECT salesagent_id
                              FROM salesagent_verticals
                             WHERE subcategory_id = 158)
   AND sa.email_enabled = 1
   AND s.user_id = sa.salesagent_id
   AND s.security_status = 'Reg'
--AND sa.email = '[email protected]'
/* AND sa.salesagent_id IN (SELECT say.salesagent_id
                              FROM salesagent_agency  say
                                   customer  c,
                                   auction2  a2
                             WHERE say.agency_id =c.agency_id
                               AND c.customer_id = a2.owner_id
                               AND auction_id = 29465)
   AND EXISTS (
       SELECT 'x'
         FROM salesagent_agency  say
              customer  c,
              auction2  a2
        WHERE say.salesagent_id = sa.salesagent_id
          AND c.agency_id = say.agency_id
          AND a2.owner_id = c.customer_id
          AND a2.auction_id = 29465)
ORDER BY 1;