code: public static function mailto($text, $email = null, $options = [])
      {
          $options['href'] = 'mailto:' . ($email === null ? $text : $email);
          return static::tag('a', $text, $options);
      }
docs: Generates a mailto hyperlink.
  @param string $text link body. It will NOT be HTML-encoded. Therefore you can pass in HTML code
  such as an image tag. If this is coming from end users, you should consider [[encode()]]
  it to prevent XSS attacks.
  @param string $email email address. If this is null, the first parameter (link body) will be treated
  as the email address and used.
  @param array $options the tag options in terms of name-value pairs. These will be rendered as
  the attributes of the resulting tag. The values will be HTML-encoded using [[encode()]].
  If a value is null, the corresponding attribute will not be rendered.
  See [[renderTagAttributes()]] for details on how attributes are being rendered.
  @return string the generated mailto link