Quote:
INVALID CHARACTERS IN HEADER

Non-encoded 8-bit data (char E9 hex) in message header 'Subject'
Subject: [MountyHall] Votre DLA est depass\351e.\n
                                           ^

This nondelivery report was generated by the amavisd-new program
at host filer. Our internal reference code for your message
is 23787-01.


WHAT IS AN INVALID CHARACTER IN MAIL HEADER?

The RFC 2822 standard specifies rules for forming internet messages.
It does not allow the use of characters with codes above 127 to be used
directly (non-encoded) in mail header (it also prohibits NUL and bare CR).

If characters (e.g. with diacritics) from ISO Latin or other alphabets
need to be included in the header, these characters need to be properly
encoded according to RFC 2047. This encoding is often done transparently
by mail reader (MUA), but if automatic encoding is not available (e.g.
by some older MUA) it is the user's responsibility to avoid the use
of such characters in mail header, or to encode them manually. Typically
the offending header fields in this category are 'Subject', 'Organization',
and comment fields in e-mail addresses of the 'From', 'To' and 'Cc'.

Sometimes such invalid header fields are inserted automatically
by some MUA, MTA, content checker, or other mail handling service.
If this is the case, that service needs to be fixed or properly configured.
Typically the offending header fields in this category are 'Date',
'Received', 'X-Mailer', 'X-Priority', 'X-Scanned', etc.

If you don't know how to fix or avoid the problem, please report it
to _your_ postmaster or system manager.


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   554 5.6.0 Message with invalid header rejected, id=23787-01 - Non-encoded 8-bit data (char E9 hex) in message header 'Subject'

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