Error in email received from registration in capitals

[xairu]

Good morning!

I've been using prestashop 1.7.5.1 and I've checked that when a costumer registers in our shop and introduces his email in capitals, the confirmation email that he gets just shows generic data. HELLO {FIRSTNAME} {LASTNAME}, THANKS TO CREATE A COSTUMER ACCOUNT {SHOP_NAME}, etc.

Did someone has the same mistake?

I think that the solution will be apply php mb_strolower function  before inserting costumer's email, but I want to know in which tpl or folder is, or if someone  would mind to show me a better solution.

Thanks in advance!