Antispam Tools

To protect your users from spam, you can use the following tools with
your Plesk:

• SpamAssassin spam filter. It is a powerful spam filter that uses
  a wide variety of local and network tests to identify spam
  signatures.

  You can configure the spam filter so as to either delete suspicious
  messages when they come to your mail server, or change the subject
  line and add “X-Spam-Flag: YES” and “X-Spam-Status: Yes” headers to
  the messages. The latter can be useful for users who prefer to filter
  mail with mail filtering programs installed on their own computers.

  To learn more about SpamAssassin, visit
  http://spamassassin.apache.org.

  To configure and switch on the SpamAssassin filter, proceed to the
  section SpamAssassin Spam Filter.

• DKIM. DKIM is a spam protection system based on sender
  authentication. When an email claims to originate from a certain
  domain, DKIM provides a mechanism by which the recipient system can
  credibly determine that the email did in fact originate from a person
  or system authorized to send email for that domain. If the sender
  verification fails, the recipient system discards such email
  messages. To configure the DKIM system on your server, refer to the
  section DKIM Protection.

• DNS blackhole lists. This spam prevention system is based on DNS
  queries made by your mail server to a database, which contains known
  and documented sources of spam, as well as an extensive listing of
  dynamic IP addresses. Any positive response from this database should
  result in your mail server returning a ‘550’ error, or rejection of
  the requested connection.

  To configure your mail server for working with DNSBL databases,
  proceed to the section DNS Blackhole Lists.

• Sender Policy Framework (available only for Linux hosting). This
  spam prevention system is also DNS query-based. It is designed to
  reduce the amount of spam sent from forged email addresses. With SPF,
  an Internet domain owner can specify the addresses of machines that
  are authorized to send email for users of his or her domain.
  Receivers that implement SPF then treat as suspect any email that
  claims to come from that domain but fails to come from locations that
  domain authorizes.

  To learn more about SPF, visit http://www.openspf.org/howworks.html.

  To enable filtering based on SPF, proceed to the section Sender
  Policy Framework System (Linux).

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