The question meant: What did the bounce say? Not what did the original message say.
I asked the same question above. It’s going to be difficult to get to the bottom of mail messages bouncing without such information as: a log of the protocol session where the message is attempted to send to Purism and/or an actual SMTP error code and message for each attempt and/or any kind of message that indicates the reason that the mail message was bounced (rejected).