[exim] NUL characters are not allowed

Hello,

We're having problems with a handful of sites that reject messages with
a 550 error, and the explanation "NUL characters are not allowed". I
know that RFC 2822 specifies that a conformant receiver must accept
messages with NUL, even though NUL is no longer allowed. What's most
irritating is that the problem tends to happen on replies to messages
that actually originated on another machine at the site that's
rejecting the message. The offending NUL appears in quoted text from
the original message.

Unfortunately, one of the people affected is the campus CIO, so I'm
making an effort to find a local workaround.

Exim version is 4.30 with exiscan-acl patch.

Thanks in advance for any help.

Jack Ziegler
Sonoma State University