Integrated SPF Best Guess. Fixes: bug #521

[exim.git] / doc / doc-txt / experimental-spec.txt

diff --git a/doc/doc-txt/experimental-spec.txt b/doc/doc-txt/experimental-spec.txt
index 15fd247ae42eb8588ed78b0db26785b4c0f12b96..4175173c320d5cf1113133a8dd7117807a152e54 100644 (file)
--- a/doc/doc-txt/experimental-spec.txt
+++ b/doc/doc-txt/experimental-spec.txt
@@ -1,4 +1,4 @@
-$Cambridge: exim/doc/doc-txt/experimental-spec.txt,v 1.10 2008/01/16 09:36:19 tom Exp $
+$Cambridge: exim/doc/doc-txt/experimental-spec.txt,v 1.11 2008/02/12 12:52:51 nm4 Exp $

 
 From time to time, experimental features may be added to Exim.
 While a feature  is experimental, there  will be a  build-time
 
 From time to time, experimental features may be added to Exim.
 While a feature  is experimental, there  will be a  build-time


@@ -799,6 +799,9 @@ variables.
   draft, this header must be added at the top of the header
   list. Please see section 10 on how you can do this.
 
   draft, this header must be added at the top of the header
   list. Please see section 10 on how you can do this.
 

+  Note: in case of "Best-guess" (see below), the convention is
+  to put this string in a header called X-SPF-Guess: instead.
+

   $spf_result
   This contains the outcome of the SPF check in string form,
   one of pass, fail, softfail, none, neutral, err_perm or
   $spf_result
   This contains the outcome of the SPF check in string form,
   one of pass, fail, softfail, none, neutral, err_perm or


@@ -808,6 +811,37 @@ variables.
   This contains a string that can be used in a SMTP response
   to the calling party. Useful for "fail".
 
   This contains a string that can be used in a SMTP response
   to the calling party. Useful for "fail".
 

+In addition to SPF, you can also perform checks for so-called
+"Best-guess".  Strictly speaking, "Best-guess" is not standard
+SPF, but it is supported by the same framework that enables SPF
+capability.  Refer to http://www.openspf.org/FAQ/Best_guess_record
+for a description of what it means.
+
+To access this feature, simply use the spf_guess condition in place
+of the spf one.  For example:
+
+/* -----------------
+deny message = $sender_host_address doesn't look trustworthy to me
+     spf_guess = fail
+--------------------- */
+
+In case you decide to reject messages based on this check, you
+should note that although it uses the same framework, "Best-guess"
+is NOT SPF, and therefore you should not mention SPF at all in your
+reject message.
+
+When the spf_guess condition has run, it sets up the same expansion
+variables as when spf condition is run, described above.
+
+Additionally, since Best-guess is not standarized, you may redefine
+what "Best-guess" means to you by redefining spf_guess variable in
+global config.  For example, the following:
+
+/* -----------------
+spf_guess = v=spf1 a/16 mx/16 ptr ?all
+--------------------- */
+
+would relax host matching rules to a broader network range.

 
 
 4. SRS (Sender Rewriting Scheme) Support
 
 
 4. SRS (Sender Rewriting Scheme) Support