gf-email-cookie.php

<?php

/*
 *
 * Save email in a cookie for ActiveCampaign
 *
 */
add_filter( 'gform_field_validation', 'tlc_save_email_cookie', 10, 4 );
function tlc_save_email_cookie( $result, $value, $form, $field ) {
  if ($field['type'] == 'email') {
    setcookie( 'email', htmlspecialchars($value, ENT_QUOTES), time() + 99999999, '/', NULL );
  }
  return $result;
}

?>