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Re: SPF in a Shared Hosting Environment (non-ISP) -> "Whitelisting only" records

2004-08-03 06:08:38
On Tue, Aug 03, 2004 at 02:53:50PM +0200, Daniel Lorch wrote:
You could add the "exists" mechanism after all your accepted smtp-servers
and log detailed DNS-queries for it (see host -t txt altavista.com). So
you have a list of potential IPs your user used to send emails. You can
present this list to your user: "look, these are the IPs trying to send
email pretending to be you. Is that really you?". And all the user has to
do is to accept the IPs or not.

Too complicated. I was thinking of a mailadress customers would simply send a 
mail to and automagically parsing out the headers with all mailservers. The 
only remining thing we would have to take care of is that they're not using 
our webmail to send this validation-mail :)

Grin. One possible problem with this approach was mentioned on this list a 
while ago: some isp's use multiple outgoing smtp servers, so sending one mail 
won't give you all of their possible outgoing ip's..

Koen

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