How to get the best time from submited values?
You should be able to use CTE (common table expression) along with the ROW_NUMBER() function to select the top 1 for each email.

See here for a short primer on ROW_NUMBER().
And here for CTE.

Something like:

WITH CTE AS (
SELECT ROW_NUMBER() OVER (PARTITION BY email ORDER BY email, datesubmission) R, *
FROM MyTable
)
SELECT * FROM CTE
WHERE R = 1
ORDER BY datesubmission, email