Fix malformed message saved into Sent folder when using big attachments and low memory limit (#6498)

CHANGELOG

@@ -19,6 +19,7 @@ CHANGELOG Roundcube Webmail
 - Elastic: Fix unwanted thread expanding when selecting a collapsed thread in non-mobile mode (#6445)
 - Elastic: Add "status bar" for mobile in mail composer
 - Log errors caused by low pcre.backtrack_limit when sending a mail message (#6433)
+- Fix malformed message saved into Sent folder when using big attachments and low memory limit (#6498)
 - Fix incorrect IMAP SASL GSSAPI negotiation (#6308)
 - Fix so unicode in local part of the email address is also supported in recipient inputs (#6490)
 - Fix bug where autocomplete list could be displayed out of screen (#6469)

program/lib/Roundcube/rcube.php

@@ -1716,7 +1716,10 @@ class rcube
             $this->smtp->disconnect();
         }
 
-        $message->headers($headers, true);
+        // Add Bcc header back
+        if (!empty($headers['Bcc'])) {
+            $message->headers(array('Bcc' => $headers['Bcc']), true);
+        }
 
         return $sent;
     }