Spam Control

Unsolicited electronic mail is colloquially known as spam. The restriction of mail based on originator is known as spam control. The SMTP proxy provides the ability to define a list of one or more restrictors that operate based on either server name (suffix) or nonserver (address range) criteria.

Spam restrictors have one of two syntactic forms:

• server suffix (suffix in a named host), or

• start address [..  end address] (range of one or more IP addresses of unnamed hosts)

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  Note -

  No spaces are permitted around the double dots (..) in this construct for the address range.

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server suffix is simply an ASCII character string.

See "SMTP Proxy Operation" for details regarding how these restrictors are used.

Spam restrictors are defined using the command-line interface, and the mail_spam subcommand of ssadm edit in the administration GUI.

The following is an example of what you would type to display the current set of spam restrictors while logged in to the primary Screen:

admin% ssadm -r primary edit Initial
edit> mail_spam list
"total-nonsense.org"
"0.0.0.0..255.255.255.255"

The above example listing shows two entries, one to refuse email from the server or servers with registered address in the domain total-nonsense.org, the other to refuse mail from any host that does not have a registered server name (in a reverse-mapping of IP address to DNS name).

The following is an example of what you would type to add an additional restriction while logged in to the primary Screen:

edit> mail_spam add complete-spam.net
edit> quit

The following is an example of what you would type to remove a restriction while logged in to the primary Screen:

edit> mail_spam delete lite-spam.com

From the command line, in addition to controlling incoming spam destined for your site, another important area of control over email is the limitation on accepting email and then relaying it to another location. Relayed mail is responsible for a great deal of the unsolicited email on the Internet. Improper relaying makes spam harder to defeat and leaves the relaying site open to various types of reprisal from the ultimate recipient-victims.

The SMTP proxy allows the configuration of a set of strings that, coupled with policy rules, enables you to restrict the destination domains that the proxy accepts.