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Kevin Spicer kevins at BMRB.CO.UK
Wed Jul 13 22:57:32 IST 2005

On Wed, 2005-07-13 at 15:57 -0400, Ugo Bellavance wrote:
> Julian Field wrote:
> > The result is that we can't publish a useful SPF record. At least I 
> > don't think we can.
> > Is there a way of publishing an SPF record that says nothing useful? :-)
> > 
> Actually, yes... if you use a tilde (~) instead of a dash (-), it only
> generates softfails...  It is almost like saying nothing useful...

In fact there are four different levels, if you really wish to make no
statement you should use ?all. Where you discourage users from sending
through other servers use ~all.  Where you are confident that all mail
originates from your servers -all.  Where you wish to indicate that mail
may originate from anywhere +all.

If you can't tie your users down to using your servers then you should
probably publish a ?all or +all.  I've done this for a couple of the
domains I look after (the others are using -all because I can).  I think
its probably a good idea to do this as MSN and hotmail are saying they
will block mail from domains without an SPF record from November.  My
understanding is that it is the presence or absence of an SPF record
that will determine if mail is blocked, reading between the lines a
permissive SPF record is acceptable.

I agree that SPF will do little for spam (especially as so much spam and
viruses now originate from zombie machines).  However where it could be
useful (depending on adoption) is in preventing joe-jobs and other
forged mail (such as from worms).  I guess this isn't as important to
ISP's (or even public sector) but as an administrator in a corporate
environment anything I can do to help protect our business from damage
to our reputation potentially caused by forged mail is welcome.  Also
anything that reduces the number of calls I get along the lines of
"Hello, I've just had a call from my client saying I sent them a virus"
is welcome ;)

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