PHPMailer::clearCustomHeader( string $name, string|null $value = null ): bool

4339    public function clearCustomHeader($name, $value = null)4340    {4341        if (null === $value && strpos($name, ':') !== false) {4342            //Value passed in as name:value4343            list($name, $value) = explode(':', $name, 2);4344        }4345        $name = trim($name);4346        $value = (null === $value) ? null : trim($value);4347 4348        foreach ($this->CustomHeader as $k => $pair) {4349            if ($pair[0] == $name) {4350                // We remove the header if the value is not provided or it matches.4351                if (null === $value ||  $pair[1] == $value) {4352                    unset($this->CustomHeader[$k]);4353                }4354            }4355        }4356 4357        return true;4358    }