diff --git a/lib/Service/Html.php b/lib/Service/Html.php
index 4d9989a3a2..61742845b6 100755
--- a/lib/Service/Html.php
+++ b/lib/Service/Html.php
@@ -120,6 +120,8 @@ public function sanitizeHtmlMailBody(string $mailBody, array $messageParameters,
 		$config->set('URI.Host', Util::getServerHostName());
 
 		$config->set('Filter.ExtractStyleBlocks', true);
+		$config->set('CSS.AllowTricky', true);
+		$config->set('CSS.Proprietary', true);
 
 		// Disable the cache since ownCloud has no really appcache
 		// TODO: Fix this - requires https://github.com/owncloud/core/issues/10767 to be fixed