Roger also had this example for me. I use a shared third party SNTP server.
This will prevent others from forging random users from my domain. They
could still forge real users.
Guy
Roger Moser wrote:
To allow only User1, User2, etc. to send mail only through 1.2.3.4 or
2.3.4.5, setup following records:
"v=spf1 exists:%{l}.%{i}._spf1.watkins-home.com -all"
User1.1.2.3.4._spf1.watkins-home.com A 127.0.0.1
User1.2.3.4.5._spf1.watkins-home.com A 127.0.0.1
User2.1.2.3.4._spf1.watkins-home.com A 127.0.0.1
User2.2.3.4.5._spf1.watkins-home.com A 127.0.0.1
...
Or you could have following records (less recommended):
"v=spf1 -exists:%{l}._spf1.watkins-home.com ip4:1.2.3.4 ip4:2.3.4.5 -all"
*._spf1.watkins-home.com A 127.0.0.1
User1._spf1.watkins-home.com TXT ""
User2._spf1.watkins-home.com TXT ""
...
Roger
-----Original Message-----
From: owner-spf-discuss(_at_)v2(_dot_)listbox(_dot_)com
[mailto:owner-spf-discuss(_at_)v2(_dot_)listbox(_dot_)com] On Behalf Of Daniel
Taylor
Sent: Wednesday, September 15, 2004 9:50 AM
To: spf-discuss(_at_)v2(_dot_)listbox(_dot_)com
Subject: Re: [spf-discuss] SPF-compliant phishing?
Hmm. Very interesting.
I should have recognized this before.
Well, it does fix Mr. Woodhouses objections, as this
mechanism would allow at least two of the forgeries he
presented to be caught, if not the lot. It is more
involved to setup however, and the additional administration
will likely prevent widespread use of the more complicated
mechanisms for a while.
Roger Moser wrote:
Daniel Taylor wrote:
SPF does not validate users.
The current syntax allows SPF to validate the local part on the envelope
sender. So it can validate users. For example:
mxout A 192.168.1.2
@ TXT "v=spf1 exists:%{l}.%{i}.spf.%{o} -all"
John.192.168.1.2 A 127.0.0.2
Mary.192.168.1.2 A 127.0.0.2
Roger
--
Daniel Taylor VP Operations Vocal Laboratories, Inc.
dtaylor(_at_)vocalabs(_dot_)com http://www.vocalabs.com/
(952)941-6580x203
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