SPF Filtering
How to get hereIMail uses Sender Policy Framework (SPF) to extend the Simple Mail Transfer Protocol (SMTP ) and Domain Name System (DNS) so IMail Server does not accept e-mail unless the sending computer is designated as a legitimate e-mail sender. This feature provides administrators increased capability to stop incoming e-mail from forged (spoofed) e-mail addresses.
To accomplish this e-mail security measure, SPF establishes a policy framework and a sender authentication scheme that verifies the identity of e-mail servers (domains) for incoming messages. SMTP receivers (such as IMail Server) use this information to evaluate whether the message is from an e-mail server that is authorized to send e-mail from the message sender. Messages that do not meet the SPF criteria are not accepted as a legitimate e-mail message and are processed according to the SPF settings selected on the SPF page.
How does SPF work?
SPF policy data is published on a DNS server in a .TXT record. DNS resolvers typically cache SPF data to reduce lookup traffic. Sender domains do not have to run new servers to advertise SPF information; instead, SPF uses the connecting client 's IP address and information from the SMTP envelope to evaluate the SPF policy document published via DNS. After the policy is evaluated, the message is classified and handled accordingly. For additional information about SPF, go to the SPF community at http://spf.pobox.com.
Example:
If a spammer forges mail from the mail server imaspammer.com and uses a different domain in the From address, such as john.doe@notaspammer.com, the receiving e-mail server checks the SPF record for notaspammer.com. If it finds that john.doe@notaspammer.com is not listed as a legitimate e-mail sender on notaspammer.com, the message fails and is processed by the SPF settings on the SPF tab.
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