Re: header inventory

On Thu, Mar 11, 2004 at 11:42:23AM +1000, Laird Breyer wrote:
> Perhaps it makes sense for the various filter writers and sysadmins
> on this list to offer an inventory of the various modifications
> each of their systems add to a message, so we can see where people
> agree and where they differ, and get to know patterns of use.

It's interesting to see the variations posted so far.  As someone
said, there is unlikely to be any agreement on specific items to
put in a header.  However, there might be some agreement on
a format into which these items can be jammed.

One thing I would like to see (that I mentioned on the main list a
while back) is version/locus information.  Each filter would supply a
tuple that uniquely identifies the filter and its location in the
delivery chain.  (None of the examples posted so far do this, although
one might be able to infer some of it by the header location in
relation to other added headers-- however I don't think people
mentioned where they were adding the headers.)  Required information
might include:

   - filter name and version
   - server name/IP information
   - delivery address or other key

(Note that multiple filters can be invoked at the same server so the
delivery address might be used to further identify the filter stage).

Beyond that identifying information, there could be specific data
produced by the filter.  An obvious format would simply be
keyword=value pairs, with some keywords having specific registered
meanings, some of which would be the version/stage information above.

e.g.:

Filtered-By:   filter=spam-pie version=3.14159 ipv4=10.0.0.1
	host=mx.example.com [email protected]
	thumbs=down
	problem="No To Line"
	problem="html-only"
	Score=12

One could encapsulate a reasonable amount of information in this sort
of header, while optionally still adding other X- headers as well,
perhaps with a requirement that those other headers be added directly
above (or below) the standard "Filtered-By" header.

mm