Справочник Пользователя для ZyXEL Communications 1000
Chapter 38 Anti-Spam
ZyWALL USG 1000 User’s Guide
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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 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 ZyWALL does not perform any more anti-spam
checking on that individual e-mail. A properly configured black list helps catch
spam e-mail and increases the ZyWALL’s anti-spam speed and efficiency.
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 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 ZyWALL does not perform any more anti-spam
checking on that individual e-mail. A properly configured black list helps catch
spam e-mail and increases the ZyWALL’s anti-spam speed and efficiency.
SMTP and POP3
Simple Mail Transfer Protocol (SMTP) is the Internet’s message transport
standard. It controls the sending of e-mail messages between servers. E-mail
clients (also called e-mail applications) then use mail server protocols such as POP
(Post Office Protocol) or IMAP (Internet Message Access Protocol) to retrieve e-
mail. E-mail clients also generally use SMTP to send messages to a mail server.
The older POP2 requires SMTP for sending messages while the newer POP3 can be
used with or without it. This is why many e-mail applications require you to specify
both the SMTP server and the POP or IMAP server (even though they may actually
be the same server).
standard. It controls the sending of e-mail messages between servers. E-mail
clients (also called e-mail applications) then use mail server protocols such as POP
(Post Office Protocol) or IMAP (Internet Message Access Protocol) to retrieve e-
mail. E-mail clients also generally use SMTP to send messages to a mail server.
The older POP2 requires SMTP for sending messages while the newer POP3 can be
used with or without it. This is why many e-mail applications require you to specify
both the SMTP server and the POP or IMAP server (even though they may actually
be the same server).
The ZyWALL’s anti-spam feature checks SMTP (TCP port 25) and POP3 (TCP port
110) e-mails. The anti-spam feature does not check (or act upon) e-mails that use
other protocols (such as IMAP) or other port numbers.
110) e-mails. The anti-spam feature does not check (or act upon) e-mails that use
other protocols (such as IMAP) or other port numbers.
E-mail Headers
Every email has a header and a body. The header is structured into fields and
includes the addresses of the recipient and sender, the subject, and other
information about the e-mail and its journey. The body is the actual message text
and any attachments. You can have the ZyWALL check for specific header fields
with specific values.
includes the addresses of the recipient and sender, the subject, and other
information about the e-mail and its journey. The body is the actual message text
and any attachments. You can have the ZyWALL check for specific header fields
with specific values.
E-mail programs usually only show you the To:, From:, Subject:, and Date:
header fields but there are others such as Received: and Content-Type:. To see all
of an e-mail’s header, you can select an e-mail in your e-mail program and look at
its properties or details. For example, in Microsoft’s Outlook Express, select a mail
and click File > Properties > Details. This displays the e-mail’s header. Click
Message Source to see the source for the entire mail including both the header
and the body.
header fields but there are others such as Received: and Content-Type:. To see all
of an e-mail’s header, you can select an e-mail in your e-mail program and look at
its properties or details. For example, in Microsoft’s Outlook Express, select a mail
and click File > Properties > Details. This displays the e-mail’s header. Click
Message Source to see the source for the entire mail including both the header
and the body.