docs/migration/2x_to_3x.md
Before 3.x.x, the local part (before the @) of the email address was case-sensitive. Therefore, [email protected] and [email protected] were considered as two different users. This behaviour was a bit confusing and not consistent with 99% of web services out there.
After 3.x.x, users are fetched from the database with a case-insensitive email search. Bear in mind though that if the user registers with the email [email protected], it will be stored exactly like this in the database (with casing) ; but he will be able to login as [email protected].
!!! danger It's super important then, before you upgrade to 3.x.x that you check if there are several users with the same email with different cases ; and that you merge or delete those accounts.