3Com 3CR3MFA-92 User Manual page 49

DCC
DCC (Distributed Checksum Clearinghouse) is a tool used to identify bulk
mail and is based on a number of servers that maintain databases of
message checksums. These checksums are derived from numeric values
that uniquely identify a message. DCC provides a simple but very
effective way to successfully identify spam and control its disposition
while updating its database with new spam message types.
Mail users and ISPs all over the world submit checksums of all messages
received. The database records how many of each message is submitted.
If requested, the DCC server can return a count of how many instances of
a message have been received. The 3Com Email Firewall uses this count
to determine the disposition of a message.
A DCC server receives no mail, address, headers, or any similar
information, but only the cryptographically secure checksums of such
information. A DCC server cannot determine the text or other
information that corresponds to the checksums it receives. It only acts as
a clearinghouse of counts of checksums computed by clients.
You must allow a connection on UDP port 6277 on your network firewall
or router to allow communications with a DCC server. If this port is not
available, DCC server calls will fail and slow down mail delivery.
Select DCC from the Mail Delivery -> Anti-Spam menu to configure DCC
settings.
Action — The action can be one of the following:
■
Just log: An entry is made in the log and no other action is taken.
■
Modify Subject Header: The text specified in Action Data will be
■
inserted into the message subject line.
Add header: An "X-" mail header will be added as specified in the
■
Action Data.
DCC
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