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ZyWALL USG 100/200 Series User’s Guide
559
CHAPTER 33
Anti-Spam
33.1 Overview
The anti-spam feature can mark or discard spam (unsolicited commercial or junk e-mail). Use
the white list to identify legitimate e-mail. Use the black list to identify spam e-mail. The
ZyWALL can also check e-mail against a DNS black list (DNSBL) of IP addresses of servers
that are suspected of being used by spammers.
33.1.1 What You Can Do in the Anti-Spam Screens
• Use the General screens (Section 33.3 on page 561) to turn anti-spam on or off and
manage anti-spam policies.
• Use the Black/White List screens (Section 33.4 on page 564) to set up a black list to
identify spam and a white list to identify legitimate e-mail.
• Use the DNSBL screens (Section 33.6 on page 568) to have the ZyWALL check e-mail
against DNS Black Lists.
• Use the Status screen (Section 33.6 on page 568) to see how many mail sessions the
ZyWALL is currently checking and DNSBL statistics.
33.1.2 What You Need to Know About Anti-Spam
White list
Configure white list entries to identify legitimate e-mail. The white list entries have the
ZyWALL classify any e-mail that is from a specified sender or uses a specified header field
and header value as being legitimate (see E-mail Headers on page 560 for more on mail
headers). The anti-spam feature checks an e-mail against the white list entries before doing
any other anti-spam checking. If the e-mail matches a white list entry, the ZyWALL classifies
the e-mail as legitimate and does not perform any more anti-spam checking on that individual
e-mail. A properly configured white list helps keep important e-mail from being incorrectly
classified as spam. The white list can also increases the ZyWALL’s anti-spam speed and
efficiency by not having the ZyWALL perform the full anti-spam checking process on
legitimate e-mail.
Black List
Configure black list entries to identify spam. The black list entries have the ZyWALL classify
any e-mail that is from or forwarded by a specified IP address or uses a specified header field
and header value as being spam. If an e-mail does not match any of the white list entries, the
ZyWALL checks it against the black list entries. The ZyWALL classifies an e-mail that