The mail client is free to put whatever crap in the Subject (and other headers and the envelope) they want, regardless of standards or usefulness. It would be unsafe to send this crap to the logs since there is a rich history of exploits against logging systems and various log analysis tools. Therefore unprintable characters - which have the greatest possibility of breaking things yet are easily filtered - are replaced in the log with "?" for safety.
I get all of that and believe it to be the most sensible thing. Now that I understand what is happening with postfix logging as explained to me in the previous reply, the issue is that postfix logging is unfolding the subject without removing the CRLF as per RFC5322 2.2.3 where it says "Unfolding is accomplished by simply removing any CRLF that is immediately followed by WSP". The CRLF isn't being removed. Id consider that a QOL request if Wietse would be so kind as to add that simple extra step of replacing 'CRLF' with '' when it unfolded the subject in postfix logging.
