X-Mailer not present on expired/bounced messages?

[kenw232]

I send a bunch of mail. I need to track each message that fails or is bounced back. So I stick a unique identifier in the X-Mailer header so that all messages that come back get piped through a script and I do what I need to. It works well for messages that are officialy denied such as User
Unknown.

But for messages that sit in the queue for the full 5 days and eventually expire get returned back with no X-Mailer anywhere present in the original message so I can't track it.

Is there a sendmail.cf setting I can turn on that simply keeps all useless header information including the X-Mailer for messages that fail and are returned from the queue?

I'm using Sendmail 8.12.4 on Linux 2.2.20.

Thanks.