-
NS - Name server record
- TXT - Text record
-
NSEC - Next Secure record
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APL - Address Prefix List
EXPLANATION
The Sender Policy Framework (SPF) is an open standard specifying a
technical method to prevent sender address forgery. More precisely, the
current version of SPF — called SPFv1 or SPF Classic — protects the
envelope sender address, which is used for the delivery of messages. See
the box on the right for a quick explanation of the different types of
sender addresses in e-mails.
(There are other solutions that
protect the header sender address or that do not care at all about who
sent the message, only who originally wrote it.)
Even more
precisely, SPFv1 allows the owner of a domain to specify their mail
sending policy, e.g. which mail servers they use to send mail from their
domain. The technology requires two sides to play together: (1) the
domain owner publishesthis information in an SPF record in the domain's
DNS zone, and when someone else's mail server receives a message
claiming to come from that domain, then (2) the receiving server can
check whether the message complies with the domain's stated policy. If,
e.g., the message comes from an unknown server, it can be considered a
fake.
Once you are confident about the authenticity of the sender
address, you can finally "take it for real" and attach reputation to it.
While IP-address-based reputation systems like Spamhaus or SpamCop have
prevailed so far, reputation will increasingly be based on domains and
even individual e-mail addresses in the future, too. Furthermore,
additional kinds of policies are planned for a future version of SPF,
such as asserting that all of a domain's outgoing mail is S/MIME or PGP
signed.
http://www.openspf.org/Introduction
SOURCE
http://www.openspf.org/Introduction
