spf-discuss
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Re: SPF syntax errors

2003-10-28 11:54:26
On Tue, Oct 28, 2003 at 10:47:48AM -0600, wayne wrote:
| In <20031028161901(_dot_)GJ17304(_at_)dumbo(_dot_)pobox(_dot_)com> Meng Weng 
Wong <mengwong(_at_)dumbo(_dot_)pobox(_dot_)com> writes:
| >
| > misspelled official directives are ignored.  publishers are expected to
| > use a validation tool.
| 
| I thought that syntax errors cause the SPF processing to be aborted
| and to return "unknown".  Is there something that overrides your
| message of <20031025012146(_dot_)GM17304(_at_)dumbo(_dot_)pobox(_dot_)com> 
that says:

Syntax errors appear to SPF clients as unknown extensions.  Unknown
extensions are ignored.

| As a related issue, I think that if multiple TXT records are found,
| only one should be used and that one should be the one with the
| highest SPF version that the client supports.  This would let people
| support newer versions of the SPF standard while letting older clients
| function as well as they can.  I don't see much good in concatenating
| TXT records.

The above paragraph assumes that there will only be one record matching
"v=spf1...".  Here is what the latest spec says.

   If multiple "v=spf1" responses are returned, the directives following
   "v=spf1" are concatenated in the order they are received.  DNS
   ordering is not guaranteed.  If directive evaluation order is
   important, SPF publishers MUST list mechanisms in a single TXT
   record.  In any case, SPF publishers SHOULD keep to a single TXT
   record; multiple responses are NOT RECOMMENDED.

   If a modifier is defined more than once, this constitutes a syntax
   error.  Upon syntax error, an SPF client MUST abort processing and
   return "unknown".  For example, "scope=envelope scope=header-from" is
   an error.

   TXT responses which do not start with "v=spf1" are ignored.

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