Fix bug where some message/rfc822 parts could not be attached on forward (#7323)

CHANGELOG

@@ -21,6 +21,7 @@ CHANGELOG Roundcube Webmail
 - Fix bug where a special folder couldn't be created if a special-use flag is not supported (#7147)
 - Mailvelope: Fix bug where recipients with name were not handled properly in mail compose (#7312)
 - Fix characters encoding in group rename input after group creation/rename (#7330)
+- Fix bug where some message/rfc822 parts could not be attached on forward (#7323)
 
 RELEASE 1.4.3
 -------------

program/steps/mail/compose.inc

@@ -958,7 +958,12 @@ function rcmail_write_compose_attachments(&$message, $bodyIsHtml, &$message_body
             $messages[] = $part->mime_id;
         }
 
-        if ($part->disposition == 'attachment' || ($part->disposition == 'inline' && $bodyIsHtml) || $part->filename) {
+        if (
+            $part->disposition == 'attachments'
+            || ($part->disposition == 'inline' && $bodyIsHtml)
+            || $part->filename
+            || $part->mimetype == 'message/rfc822'
+        ) {
             // skip parts that aren't valid attachments
             if ($part->ctype_primary == 'multipart' || $part->mimetype == 'application/ms-tnef') {
                 continue;