spf-discuss
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draft 02.9 comments

2003-12-04 06:24:31
I finally got around to reading the current draft and have some minor comments that focus on compaction. From what I can tell effort is being made to pack a lot of info into small amount of space (512 bytes). My suggestions take this view in addition to looking at how I would like to parse it as a programmer:

a) Conerning "v=spf1". Start the record directly with the type/version tag "spf1". In other words drop the v= prefix. Since all information is process ed left to right and we know the version must start the record, why do you need to point it out with "v="? If you were doing an xmlish style attribute list where they can appear in any order I might understand, but I thinks its pretty clear.

        v=spf1 ?all

becomes

        spf1 ?all


b) The default result. Why bother with an "all" mechanism, when the default result could be specified as part of the version tag:

        spf1 ?all

becomes

        ?spf1

c) Concerning "exp=". This is appears to be more default supplemental infomation in the case of failure. Could this be merged with the version and default result? For example:

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

becomes

        -spf1=explain._spf.%{d} mx

Hmm. On second thought I don't see the need for "exp=" modifier now nor would I implement it (drop MUST requirement for "exp"). An SPF client implementation should be left to report its own interpretation of a failure to the sender or use predefined messages specified by the SPF specification. This avoid further TXT lookups. Also these messages probably appear in mail logs and so would be useful to statistics gathering software if they were standardised either by the implementation or the specification.

d) The Received-SPF header. Drop this header and have this infomation folded into the regular Received header, which already allows for arbitrary name/value pairs in the name-val-list and comments. The added advantage to this is that it can be seen which servers support SPF.

    Received: from wks.ch (lsne-dhcp-5-51.urbanet.ch [195.202.205.51])
        by pop.snert.net spf pass (extra commentary) id hB48F1b9014462
        for <achowe(_at_)snert(_dot_)com>; Thu, 4 Dec 2003 09:15:03 +0100

If you feel that a Received-SPF is really necessary then include trace information such as server name, ip, and timestamp so that multiple instances of this header can be followed:

        Received-SPF: error by pop.snert.net [193.41.72.72];
                 Thu, 04 Dec 2003 09:15:01 +0100


--
Anthony C Howe                                 +33 6 11 89 73 78
http://www.snert.com/       ICQ: 7116561         AIM: Sir Wumpus

"...simplicity is a goal of good design,
                     it is never the starting point." - Dan Geer

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