We are receiving the following error when messages with 'bare linefeeds' try to get delivered to out journaling mailbox.

400 4.4.7 The server responded with:550 5.6.2 SMTPSEND.BareLineFeedsAreIllegal; message contains bare linefeeds, which cannot be sent via DATA. The failure was replaced by a retry...

It seems that these messages aren't making it to the Journaling mailbox. Any way to get these delivered?

Is that journal mailbox an Exchange mailbox or a journal system?

This client is sending to an external mailbox for journaling. Other clients use an internal journaling mailbox - and seem fine. Think it's getting stopped on the send connector, maybe?

Well, if the external mailbox is dropping the messages, you should contact their vendor.