I can't receive test email or sign-up email with free.fr email adress

Hi,
I’m experiencing a problem with my app. I have users, they didn’t have problems to register.
I try to register with an free.fr email I often use for tests like “xxx@free.fr” and I never receive the verification code. Searched in junks, spam, commercial, social folders : nothing.
So I tried to send a test email (found in notifications templates / one-time code). My account email is also a free.fr account and… I don’t receive the test email.

I tried to add the default email sender as “accepted mails” but I still don’t receive anything. I added soft.add domain too.

Additionnal info: I do receive mails form softr.io so I guess the problem is in my app configuration ?

If anyone has an idea for me, it will help a lot!