THE VIRTUAL SERVER HANDBOOK

Unsolicited Commercial E mail

While commercialization of the Internet has brought many benefits, among

the negative effects is the proliferation of unsolicited commercial E mail,

often called "spam."  The Virtual Server controls spam in the following

manner:

Blocking spam from being sent to users on the virtual server.

Blocking spam from being sent through the virtual server (relaying).

Blocking Incoming Spam

Defending the Virtual Server from receiving spam is tricky. One method for

blocking spam is to enter the return address on the spam in the

~/spammers

 file on the virtual server.

To block E mail from specific hosts

1.

From your Virtual Server 

~/etc/spammers

 file, enter

username@hostname

 or

hostname

(where "username" is the username of the sender and "hostname" is the

hostname portion of the sender s address, often just a domain name)

2.

From the command prompt enter 

vnewspammers

. This action

rebuilds the 

~/etc/spammers.db

 file so that changes can take

effect.

Maintaining the ~/etc/spammers file

When choosing values to place in the 

~/etc/spammers

 file, you should

understand the layout and contents of the mail message headers in an

unsolicited message. Understanding the layouts of mail messages (as read

by your Virtual Server) enables you to locate and recognize the message's

SMTP envelope sender.

Your Virtual Server places the SMTP envelope sender address in the header

line that begins with "From " (the word "From" followed by one space

character).

Notice that the differences between "From" and "From:" Header lines are

not required to be the same, although they often are. The "From:" header

line is part of the message content, not part of the SMTP envelope. If a

discrepancy exists between the "From " address and the "From:" address,

use the "From " address as your value for inclusion in the

~/etc/spammers

 file.

Envelope sender blocking is useful, but not foolproof. Since the envelope

sender can be and often is falsified by spam purveyors, the blocking can be

circumvented. However, many messages are deflected, so the effort is not

entirely wasted, provided you vigilantly maintain the 

~/etc/spammers

file.

COPYRIGHT 

 1999  DIGITAL TOOLS  LLC.

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