Mailing List Archive: Potential Problem with the SPF Explanations

In section 3.2 of the SPF spec, we have the following statements.

> Each directive is considered in turn from left to right.
> When a mechanism is evaluated, one of three things can happen: it
> can match, it can not match, or it can throw an exception.
> If it matches, processing ends and the prefix value is returned as
> the result of that record.

But then in section 5.2, regarding Explanations, there is an example SPF
record:

> v=spf1 mx -all exp=explain._spf.%{d}

Shouldn't processing of this record end when the -all directive is
processed? But this would mean that the exp= directive would never be
processed. Shouldn't domain administrators put their exp= directives ahead
of any directives that could cause a "fail" or "softfail" to occur? Or does
the SPF spec need to be clarified with respect to the way that directives
are processed?

Daryl Odnert
Tumbleweed Communications
Redwood City, California

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On Tue, Apr 13, 2004 at 03:30:37PM -0700, Daryl Odnert wrote:
|
| But then in section 5.2, regarding Explanations, there is an example SPF
| record:
|
| > v=spf1 mx -all exp=explain._spf.%{d}
|
| Shouldn't processing of this record end when the -all directive is
| processed? But this would mean that the exp= directive would never be
| processed. Shouldn't domain administrators put their exp= directives ahead
| of any directives that could cause a "fail" or "softfail" to occur? Or does
| the SPF spec need to be clarified with respect to the way that directives
| are processed?

we had a thread about this recently, the upshot was the text changed to

A meaningful modifer such as "exp" may appear to the
right of a terminal mechanism such as "all". SPF parsers
may therefore choose to extract all the modifiers from a
record before interpreting mechanisms. Alternatively,
they may continue to parse a record in search of a
meaningful modifier even after mechanism evaluation has
completed.

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