How to select only id by the unique value of other table

Question

I have a table customers. How can I select only ids for the distinct values in the email column?

+----+------------------+
| Id | Email            |
+----+------------------+
| 1  | sergiy@gmail.com |
| 2  | bob@gmail.com    |
| 3  | anre@gmail.com   |
| 4  | sergiy@gmail.com |
| 5  | antony@gmail.com |
+----+------------------+

So the result will be:

[1,2,3,5]

So far, I've tried:

select distinct id, email from customers group by id;

Answer 1

select min(id) from Customers group by email;