Ignore 'Sender' header on Reply-All action (#6506)

CHANGELOG

@@ -6,6 +6,7 @@ CHANGELOG Roundcube Webmail
 - Avoid Referer leaking by using Referrer-Policy:same-origin header (#6385)
 - Removed referer_check option (#6440)
 - Use constant prefix for temp file names, don't remove temp files from other apps (#6511)
+- Ignore 'Sender' header on Reply-All action (#6506)
 - Update to TinyMCE 4.8.2
 - Plugin API: Added 'raise_error' hook (#6199)
 - Plugin API: Added 'common_headers' hook (#6385)

program/include/rcmail_sendmail.php

@@ -1027,15 +1027,8 @@ class rcmail_sendmail
                 if ($v = $message->headers->cc) {
                     $fvalue .= (!empty($fvalue) ? $separator : '') . $v;
                 }
-                // Use Sender header (#1489011)
-                if ($v = $message->headers->get('Sender', false)) {
-                    // Skip common mailing lists addresses: *-bounces@ and *-request@ (#1490452)
-                    if (empty($message->headers->others['list-post'])
-                        || !preg_match('/-(bounces|request)@/', $v)
-                    ) {
-                        $fvalue .= (!empty($fvalue) ? $separator : '') . $v;
-                    }
-                }
+
+                // Deliberately ignore 'Sender' header (#6506)
 
                 // When To: and Reply-To: are the same we add From: address to the list (#1489037)
                 if ($v = $message->headers->from) {