[Mimedefang] Received headers in general

David F. Skoll dfs at roaringpenguin.com
Tue May 22 21:30:03 EDT 2012

On Tue, 22 May 2012 17:41:05 -0700 (PDT)
kd6lvw at yahoo.com wrote:

> You completely missed what I said earlier.  That part applies to
> NON-SMTP headers and says that we cannot and must not reject headers
> from other transports on the grounds that they don't meet SMTP's
> syntax. It doesn't apply to headers which fall under SMTP
> environment or generation, nor do I enforce SMTP syntax compliance on
> non-SMTP generated headers.

That's not how I read the RFC.

It says as one consequence of non-SMTP environments, there may be
noncompliant Received: headers.  It says a receiver MUST NOT reject
mail because of noncompliant trace headers.  It doesn't say you CAN
reject noncompliant trace headers if you (somehow?) know they were
inserted under SMTP.

> 4.4.  Trace Information

Yes, I know what a sender MUST do.  You are ignoring what a receiver

> Exchange and gmail claim SMTP transport but fail to follow the
> required syntax.  RFC 5321 does not ban rejecting on that basis.

What part of:

"receiving systems MUST NOT reject mail based on the format of a trace
header field"

is unclear?  It doesn't say MUST NOT reject mail based on the format
of a trace header field inserted by a non-SMTP protocol.  It says MUST
NOT, period.

> Where "MUST" is given, such means that there is something to
> enforce.  I enforce it and get much less spam as a result.  You don't
> and you get spammed.  That's your problem.

But I don't get spammed, so it's not my problem.  I use actual working
anti-spam techniques to combat spam rather than fascist RFC
interpretations that might let me giggle with glee over the ignorance
of Microsoft but actually stop hardly any spam.

I also happen to receive lots of legitimate mail that makes my company
quite a bit of money that would be lost were I to be as pedantic as
you, so... who has the problem, again?

(As per another poster's request for disclosure: I run servers that
process about 600K messages/day.  Across our entire customer base, our
software processes probably 60M messages/day.  How many messages/day
do you place at risk with your policies?)



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