8-bit characters are not allowed in the headers of an RFC 822 message.

We're not about to consider a patch to "fix" the problem of replacing 8-bit characters with 'X's that doesn't atleast supply a default character set and properly QP-encode the nonconforming header.

Another possiblity is suggested by Chris Newman:

The correct long term thing to do is to interpret unlabelled 8-bit as UTF-8 if it meets the UTF-8 syntax, and otherwise give it the "unknown" charset label and downconvert to 7-bit using RFC 2047. If you want to do something really fancy, you might allow a mapping from the hostname in the envelope from address to a default 8-bit charset (Innosoft's MTA includes an equivalent facility) so the administrator can set up private agreements with specific hosts.

-- RobSiemborski? - 24 Jul 2003