[Mimedefang] Looking for an explanation of "suspicious_chars"

[Cormack, Ken]

Group,

I'm looking to offer my helpdesk an explanation of why a user's expected
inbound email is being discarded because of MIMEDefang's "suspicious_chars"
check, in filter_begin.  I'd explained basically that there could be a
carriage-return or other character found in a line within the header of the
email, where that particular character is not "expected" to be found.

Without seeing the problem header in question, would that answer be too
general to help the sender find and fix the problem?  At this point in time,
I do not yet know what client mail engine, home-grown program code, or other
MUA is constructing the header in question.  But if the original answer I
gave my staff is not specific enough to assist in debugging the software
building the header, can anyone suggest a "better" answer that I may pass
along?


Thanks

Ken