We don't receive WorkMail journal records for replies

I setup WorkMail journaling email address to receive journal records. We successfully receive journal records when messages are sent to WorkMail users (we're calling this the inbound first touch), and records are delivered when WorkMail users send email (outbound first touch). We don't, however, get records delivered when the WorkMail user either replies to messages they receive, nor when an outside user replies to a WorkMail user. We only get records for the initial, "first touch" message. This doesn't seem like desired behavior. Is it? I know the email addresses work because we get the first message. Just not the replies.