GroupBy Email & get earliest created_at date in Group - Laravel Eloquent - php

Question

How can I get the earliest created_at date when using groupBy in an eloquent statement?
I have a table with the following:
| id | name | email | created_at |
|----|--------|---------|---------------------|
| 1 | test | 1#1.com | 2018-01-01 09:00:00 |
| 2 | test | 1#1.com | 2018-01-02 09:00:00 |
| 3 | test 2 | 2#2.com | 2018-01-02 09:00:00 |
| 4 | test 2 | 2#2.com | 2018-01-03 09:00:00 |
| 5 | test | 1#1.com | 2018-01-03 09:00:00 |
| 6 | test | 1#1.com | 2018-01-04 09:00:00 |
| 7 | test | 1#1.com | 2018-01-05 09:00:00 |
| 8 | test 3 | 3#3.com | 2018-01-06 09:00:00 |
| 9 | test 3 | 3#3.com | 2018-01-07 09:00:00 |
when running the following query:
Customers::OrderBy('created_at', 'desc')->groupBy('email')->paginate('5');
I was expecting to get the results in the following order:
Test 3 (created: 2018-01-07)
Test (created: 2018-01-05)
Test 2 (created: 2018-01-03)
But instead I am getting so it doesn't look like it's respecting the OrderBy
Test 3 (created: 2018-01-06)
Test 2 (created: 2018-01-02)
Test (created: 2018-01-01)
Here is the SQL fiddle
http://sqlfiddle.com/#!9/89ee39/2
# EDIT - Answer based on response
Thanks to Nesku, finally query to get this working was:
return DB::table('customers')
->select(DB::raw('email, max(created_at)'))
->groupBy('email')
->orderBy('max(created_at)', 'desc')
->get();

Answer 1

You can't order by created_at because it contains multiples values, you can however take the max of created_at for each email and order by that.
The SQL query would look like this :
SELECT email, max(created_at)
FROM `customers`
GROUP BY email
ORDER BY max(created_at) DESC
http://sqlfiddle.com/#!9/89ee39/12