From: Wietse Venema (no email)
Date: Wed Feb 05 2003 - 16:54:45 EST
:
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> On Wed, 5 Feb 2003, Laurent Wacrenier wrote:
>
> > Wietse Venema wrote:
> > > So what problem are you talking about?
> >
> > On client.example.org, send a mail like this :
> >
> > true | mail -s '____'
> >
> > The mail is accepted by sendmail, who just drop it the queue, but
> > is rejected by cleanup and a bounce is generated for
> > . As example.org domain mail is managed by
> > server.example.org, the bounce goes here. But, as the bounce containts
> > improper 8-bit header in a MIME part, it's also rejected and the mail
> > vanish.
> >
>
> So don't reject 8bit MIME content :-) Are you asking for Postfix to be
> more liberal when handling "Content-Type: multipart/report"? This is
> arguably reasonable. Since the 8bit content is detected by the MIME
> parser, and the bounced message content is located inside an outer
> "multipart/report" structure, it is possible in principle to protect the
> nested content from 8bit sanity checks.
>
> Would being liberal with bounces make rejecting 8bit content useful to
> you. Despite the RFCs such content is quite common, so rejecting it is
> impractical for most sites. It is not clear that "fixing" 8bit bounce
> processing is worth the extra cost.
>
> Your setup is relatively complex: local users injecting mail with
> non-local sender addresses, but perhaps not too unusual for a
> campus network of UNIX machine with a single user namespace and
> centralized mail hubs.
>
> Wietse what do you think, should MIME checks special-case multipart/report
> to cater for mail-hub environments where $myorigin (perhaps after
> masquerading) does not match $mydestination?
It's no good because a lot of software (qmail, Majordomo, Postfix<2.0)
does not MIME encapsulate bounces by the book, and therefore 8-bit
content can show up unexpectedly in headers or bodies.
Because of this, the strict 7-bit features in Postfix are not as
useful as one would expect. It might be more useful if there were
tolerance levels, like allowing some percentage of header or body
content to be in violation before rejecting the mail.
Wietse
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