Thanks everyone for your quick answer.
Just kidding, of course i didn't get any answer of this forum.
I am really looking for a forum that DOES answer people's questions, if anyone knows any, please PM me : i'm sick of never getting answers...
Anyway, I found the answer on another forum :
You need to edit wp-login.php in some way, and add the following lines :
`// Check that the e-mail address is an '@the_email_you_want.com' adress
if ( ! preg_match ('#^[\w.-]+@the_email_you_want.com$#',$user_email )) {
$errors->add( 'invalid_email', __( '<strong>ERROR</strong>: Type your error message here ' ) );
$user_email = '';
}
// End of Ieseg verification`
Sadly, this doesn't work when you have some additional registration plugin enabled, such as the great "theme_my_login", so I have the choice of either not using it, or forgetting about email domain verification.
Maybe I could implement it in the "theme_my_login" plugin file, but I can't find the corresponding fonction, and I won't ask the question on this forum because I know it would be a loss of time ..
Anyway, I hope that helped the many people who are in the same desperate situation :)