From: Filippo Tessarotto <zoeslam@gmail.com>
Date: Fri, 29 Dec 2017 16:30:07 +0100
Subject: [PATCH] Fix idn_to_ascii deprecation warning

--- a/src/Header/AbstractAddressList.php
+++ b/src/Header/AbstractAddressList.php
@@ -102,6 +102,9 @@ public function getFieldName()
     protected function idnToAscii($domainName)
     {
         if (extension_loaded('intl')) {
+            if (defined('INTL_IDNA_VARIANT_UTS46')) {
+                return (idn_to_ascii($domainName, 0, INTL_IDNA_VARIANT_UTS46) ?: $domainName);
+            }
             return (idn_to_ascii($domainName) ?: $domainName);
         }
         return $domainName;