240a241
>     my $message_id = $args{'MIMEObj'}->head->get('Message-Id');
244a246,247
>     $RT::Logger->debug("Message-ID: $message_id");
>     # the colons are necessary to make ->build include non-standard headers
251,252c254,256
<         Precedence             => 'bulk',
<         'X-RT-Loop-Prevention' => $RT::rtname,
---
>         'Precedence:'             => 'bulk',
>         'X-RT-Loop-Prevention:' => $RT::rtname,
>         'In-Reply-To:'          => $message_id,