Blocking unwanted messages in Majordomo

Majordomo's filtering looks for character strings (words) defined by the administrator. If a defined word is found, the message is sent to the administrator as what is referred to as a BOUNCE message. The administrator either accepts or rejects the message. An approved message is forwarded to the list.

Keywords are defined in two lists: taboo body and taboo headers. The words defined in taboo body are searched for from the message's body text, whereas the words defined in the list for taboo headers are searched for from the message's header data. Header data includes the fields From, To and Subject, as well as the message's transmission data.

The keyword lists are defined as follows:

• Go to http://majordomo.helsinki.fi
• Sign in with your own user name and password
• Enter the name of the list in section List Name (without quotation marks and the @helsinki.fi part of the name)
• Enter the administration password in section Admin Password
• In section Modify What?, select Configuration Options
• In the drop-down menu on the top of the page, select All keywords
• Find the section for taboo body and taboo headers and add the expressions you wish to ban
• Finally, click Apply
• The response message will arrive to the address marked in the adjacent field.

The university's centralised spam recognition improves Majordomo filters' ability to prevent spam from getting on the lists. Linking the keyword X-HY-Spam-Status to the taboo_headers list allows for finding all messages identified as possible spam (see the first example on the following list).

Examples of Majordomo's taboo expressions

You can come up with more expressions as you wish.

• each keyword is presented on its own line
• each character string is usually preceded and followed by a slash ( / )
• an i following the ultimate / character refers to case insensitivity; without it, "SPAM" and "Spam" are construed as different words
• if a word includes the / character, it should be preceded by a backslash ( \ ) in this fashion: \/
• \s refers to a space
• the dot ( . ) stands for any character
• the asterisk ( * ) stands for an arbitrary number of the preceding character – in other words, \s* indicates an arbitrary number of spaces and .* an arbitrary number of any character
• the backslash ( \ ) can be used in front of special characters such as the asterisk, dot or slash, in which case they lose their special significance

Non-subscribers are barred from sending mail as follows

• Go to http://majordomo.helsinki.fi
• Sign in with your own user name and password
• Enter the name of the list in section List Name (without quotation marks and the @helsinki.fi part of the name)
• Enter the administration password in section Admin Password
• In section Modify What?, select Configuration Options
• In the drop-down menu on the top of the page, select All keywords
• Find restrict post, write the name of the list (e.g. humppa-lista), watch out for misspellings!
• Finally, click Apply
• The response message will arrive to the address marked in the adjacent field.

This will allow only subscribers' mails through. Any messages sent by other people will first go to the administrator for approval. For further information on the approval of messages, see section Forwarding BOUNCE messages to the list.

What is problematic about this method is that it requires subscribers to use precisely the same address for sending mail as they did when they subscribed to the list. Many people either cannot or will not make this setting in their email client. This results in unnecessary delays in message delivery and more work for the administrator.

It is also possible to pre-define a small group of addresses which are the only addresses from which mail is allowed through. The restrict_post field is actually a file name. In Majordomo, the email list's addresses in the file the name which corresponds with the list's name. You can also enter some other file name in the field, such as a file located in your own home directory, e.g. /h/2/tkol/iankka/testi-lista.senders.txt. The addresses from which mail is allowed through are listed in the file, one address per line. This method allows the administrator to specify whose mail is allowed through to the list. Employing this method requires the IT Center's Unix license.

List moderation constitutes a kind of pre-censorship. All messages go through the administrator for approval. This is a convenient way to monitor all mails sent to the list, should that be necessary.

• Go to http://majordomo.helsinki.fi
• Sign in with your own user name and password
• Enter the name of the list in section List Name (without quotation marks and the @helsinki.fi part of the name)
• Enter the administration password in section Admin Password
• In section Modify What?, select Configuration Options
• In the drop-down menu on the top of the page, select All keywords
• Find moderate and select yes
• Finally, click Apply
• The response message will arrive to the address marked in the adjacent field.

Moderation requires the administrator to monitor the list constantly, so that messages are not unduly delayed. For more on how to approve messages, see section Forwarding BOUNCE messages to the list.

Pre-approval of messages

Moderation also requires that any messages sent by the administrator have to be approved for the list separately. Messages can also be sent by bypassing moderation and other filtering methods. This takes place by adding, at the beginning of the message, the line

Approved: password.

• at the top (as the first line) of one's own message, in which case it must be followed by an empty line,
• or in the headers of messages, provided that your email client supports this option.

The Pine client supports the latter option if you add the word Approved under customized-hdrs in the client's settings. When writing the message, you must press Ctrl+R in the header field and enter your password.