Re: [exim] NUL characters are not allowed

On 10/13/2004 8:20, "Jack Ziegler" <ziegler@???> wrote:

> 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.

We run incoming mail through a bunch of code written here. When we started
having NULs in incoming messages break people's POP and IMAP retrievals of
the messages (which were spam when we saw the problem several months ago,
with the NULs tagging along at the ends of MIME parts) we added NUL
stripping to that code.

(That would break signed messages, but so far that hasn't been an
issue...presumably signed messages are prepared without NULs, and most of
our users don't participate in signed messages anyhow.)

Given Exim's current ability to tell you how many NULs there are in a
message (the only right answer is 0), rejecting messages with NULs from the
world at SMTP time would be attractive. Although as you've noticed, that
would export the problem...probably to someone else's CIO. ;-)

--John