Anti-Spam; Overview; What You Can Do In This Chapter; What You Need To Know - ZyXEL Communications ZyWall USG20-VPN User Manual

28.1 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 USG can also
check e-mail against a DNS black list (DNSBL) of IP addresses of servers that are suspected of
being used by spammers.

28.1.1 What You Can Do in this Chapter

• Use the Profile screens
spam policies.
• Use the Mail Scan screen
functions.
• Use the Black/White List screens
spam and a white list to identify legitimate e-mail.
• Use the DNSBL screens
Black Lists.

28.1.2 What You Need to Know

White List
Configure white list entries to identify legitimate e-mail. The white list entries have the USG classify
any e-mail that is from a specified sender or uses a specified header field and header value as being
legitimate (see
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 USG 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
USG's anti-spam speed and efficiency by not having the USG 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 USG 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 USG checks it against
the black list entries. The USG classifies an e-mail that matches a black list entry as spam and
immediately takes the configured action for dealing with spam. If an e-mail matches a blacklist
entry, the USG does not perform any more anti-spam checking on that individual e-mail. A properly
(Section 28.3 on page
(Section 28.4 on page
(Section 28.5 on page
(Section 28.7 on page
E-mail Headers on page 436
USG20(W)-VPN Series User's Guide
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HAPTER
437) to turn anti-spam on or off and manage anti-
440) to enable and configure the mail scan
442) to set up a black list to identify
447) to have the USG check e-mail against DNS
for more on mail headers). The anti-spam feature
435
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Anti-Spam