SPF: Its Functionality and How To Use It On Your Server
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Last week, we heard about how Yahoo! and Microsoft are making a big push to develop anti-spam technologies. These will soon be standards that hosts will need to implement in order to provide a reliable mail service. This week, we take a look at exactly how a host can be well prepared by implementing SPF technologies.
Introduction
One of the major difficulties in today’s battle with spam email lies in the fact that it is a simple matter for a spammer to create an email message that impersonates any domain the spammer wants. There hasn’t been any way for domain owners to specify what servers are allowed to send mail for a certain domain in order to prevent this kind of impersonation.
Of course, MX DNS records tell internet servers what IP addresses receive mail for a domain, but they don’t always define all the servers that can send mail for a particular domain. For instance, perhaps all incoming mail for a certain domain must pass through a certain server, but what if a webserver or network device sends email notifications to e-commerce customers? This prevents MX records from being successfully used as a reliable list of authorized servers that send mail from a specific domain.
In answer to this problem, we have SPF, or Sender Policy Framework. SPF is a way for domain owners to publish servers that are authorized to send email from a specific domain so that any other email servers on the internet can reliably look up the authorized servers’ IP addresses.
Next: SPF Basics >>
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