On Mon, Nov 20, 2023 at 11:02:15AM -0500, postfix--- via Postfix-users wrote:
> > You'd need to apply "body checks" to internally generated mail, which is
> > generally not recommended, and would apply regardless of context, not
> > just to bounced header-only content.
> >
> > main.cf:
> > internal_mail_filter_classes = bounce
> > bounce_body_checks = pcre:{ {~^(Content-Type:\s*multipart/)~
> > X-$${1}} }
> >
> > master.cf:
> > bounce unix - - n - 0 bounce
> > -o { cleanup_service_name = bounce-cleanup }
> > bounce-cleanup unix n - n - 0 cleanup
> > -o { receive_override_options = no_milters }
> > -o { disable_mime_input_processing = no }
> > -o { body_checks = $bounce_body_checks }
> > -o { header_checks = }
> > -o { nested_header_checks = }
> >
>
> Thank you! This might work for us (and does for this specific test case).
> But do I read you right that the danger is that if the full message is
> returned in the third part of the report then this setup would alter those
> headers as well (which would then presumably break the message, since it's
> not meant to be headers-only)?
No. This will not break actual MIME headers in the returned message, but
may interfere with message content where the string:
Content-Type: multipart/mumble
occurs at the beginning of a message body line in contexts other than
returned headers. Note that the configuraion is narrowly targetting
just the "bounce" service, and enables only "body_checks". It is
as safe as I know how to make it...
The caveat is there to let you know that the rule is less surgically
precise than say a tailored Postfix feature to explicitly censor or
modify the headers to be included in a header-text-only bounce.
Given infinite cycles, Postfix would support some sort of
"header-checks" like syntax for deciding how to tweak the returned
headers. But the cost here should be borne by the guilty party (Amazon)
and not Postfix.
Barring more compelling use-cases, We should not go out of our way to
help their broken MTA work.
--
Viktor.
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