LEFT OUTER JOIN and WHERE EXISTS. Are they equivalent?

Question

I would like to create equivalent MySQL query using LEFT OUTER JOIN to WHERE EXISTS. I am following this question:

Are the SQL concepts LEFT OUTER JOIN and WHERE NOT EXISTS basically the same?

This is the original query:

SELECT *
FROM tableA
JOIN tableB ON tableA.tableA_id = tableB.tableB_id
JOIN tableC ON tableC.tableC_id = tableB.tableB_id
WHERE  NOT EXISTS (
    SELECT 1
    FROM tableD
    WHERE tableA.employee_id = tableD.employee_id AND tableC.tableC_datum = DATE(tableD.tableD_od_datetime)
)

But this query return different values:

SELECT *
FROM tableA
JOIN tableB ON tableA.tableA_id = tableB.tableB_id
JOIN tableC ON tableC.tableC_id = tableB.tableB_id
LEFT OUTER JOIN tableD ON tableA.employee_id = tableD.employee_id AND tableC.tableC_datum = DATE(tableD.tableD_od_datetime)
WHERE tableD.employee_id IS NULL AND DATE(tableD.tableD_od_datetime) IS NULL

Why are these two outputs not equivalent, please?