Show the preheader in the newsletter preview

newsletter-bundle/contao/classes/Newsletter.php

@@ -298,8 +298,9 @@ public function send(DataContainer $dc)
     <td>' . implode(', ', $arrAttachments) . '</td>
   </tr>' : '') . '
 </table>' . (!$objNewsletter->sendText ? '
-<div class="preview_html">
-' . $html . '
+<div class="preview_html">' . ($objNewsletter->preheader ? '
+<p class="preheader">' . $objNewsletter->preheader . '</p>' : '') . '
+' .$html . '
 </div>' : '') . '
 <div class="preview_text">
 <pre style="white-space:pre-wrap">' . $text . '</pre>
@@ -403,6 +404,11 @@ protected function generateEmailObject(Result $objNewsletter, $arrAttachments)
 	 */
 	protected function sendNewsletter(Email $objEmail, Result $objNewsletter, $arrRecipient, $text, $html, $css=null)
 	{
+		if (\count(func_get_args()) > 5)
+		{
+			trigger_deprecation('contao/newsletter-bundle', '5.3', 'Passing CSS to the Newsletter::sendNewsletter() method has been deprecated and will no longer work in Contao 6. Add the CSS in the template instead.');
+		}
+
 		$simpleTokenParser = System::getContainer()->get('contao.string.simple_token_parser');
 
 		// Newsletters with an unsubscribe header are less likely to be blocked (see #2174)