http://old.openspf.org/index.html is a great little site. To quote the site:
SPF is Sender Policy Framework
SPF fights return-path address
forgery and makes it easier to identify
spoofs.
Domain owners identify sending mail servers in DNS.
SMTP receivers verify the envelope sender address against
this information, and can distinguish authentic messages from
forgeries before any message data is transmitted.
I setup a SPF record in my public DNS server. It looks something like:
The SPF record:
v=spf1 a include:mymailisp.com ~all
can be explained as:
![[v=spf1]](http://old.openspf.org/images/label_v=spf1.png) |
v=spf1 |
This identifies the TXT record as an SPF string. |
 "> |
a |
sol3.net's IP address is 72.19.149.196
(72-19-149-196.static.myisp.net).
That server is allowed to send mail
from sol3.net. |
![[include:]](http://old.openspf.org/images/label_include:.png) |
include:mymailisp.com |
Any server allowed to send mail from mymailisp.com is also
allowed to send mail from sol3.net. |
![[all]](http://old.openspf.org/images/label_all.png) |
~all |
SPF queries that do not match any other mechanism will return "softfail".
Messages that are not sent from an approved server should still be accepted
but may be subjected to greater scrutiny. |