Hello @Discover Me 360 (DM3) !

Both points should be checked separately. The first one can be looked through the sys_accounts table. If there is no such email then it needs to check the view then it needs to review the email itself - maybe it's not accepted by the common Regex rules of the email validator:

static public function checkEmail($s)

    {

        if (false === strpos($s, '@') || strpos($s, '@') != strrpos($s, '@')) // simple check

            return false;

        if (!preg_match("/^[\pL\pNd]/u", $s)) // must start with letter or number

            return false;

        if (!preg_match("/@[\pL\pNd\.\-]+$/u", $s)) // validate domain

            return false;

        if (!getParam('sys_account_allow_plus_in_email') && false !== strpos($s, '+'))

            return false;

        $s = str_replace(array('@', '.', '-', '+', '_'), '', $s); // allowed symbols

        if (preg_match("/[^\pL^\pNd]/u", $s)) // check for undesirable chars

            return false;

        return true;