I am making a WordPress plugin. I have to create a Name and email checker.
i have a form with POST method. In this form you fill your email and name

<form method="post">
        <input type="text" name="yourname" placeholder="name" required>
        <input type="text" name="mail" placeholder="email" required>
        <input class="btnAdd" type="submit" value="Add">
    </form>

Then i want to make a sql query to check if there is a user with the email that has been filled in. i console.log’d $EmailCheckResults from below here. and it gives this back:
SELECT user_email FROM users WHERE user_email = 0

global $wpdb;
        
        $emailToCheck = $_POST['mail'];     
        $EmailCheckResults = $wpdb->prepare("SELECT user_email FROM users WHERE user_email = %d", $emailToCheck);
        $CheckResults = $wpdb->get_var($EmailCheckResults);

any ideas why %d is 0? even if i fill in the email input