Topics= topic1,topic2,...topic23

This feature and keyword are not available in LISTSERV Lite.

List topics provide a way to run a mailing list (preferably moderated) where several sub-topics are being discussed in parallel but some subscribers are only interested in a subset of the topics. For instance, a working group might have general discussions, decisions, and messages related to meetings. People who cannot attend the meetings can then opt out of last calls for hotel reservations and discussions about seafood restaurants, whereas people who have no time to follow the discussions can elect to get just the decisions. At any rate, such a compartmented list requires a certain discipline in order to be successful, as the posters must label their messages to indicate which topic(s) they belong to.

Through the Topics= keyword, the list owner can define up to 23 topics for the list (note that 1.8c and earlier are limited to 11 topics). For instance, the list owner could code:

* Topics= News,Benchmarks,Meetings,Beta-tests

If necessary, you may use multiple Topics= lines in your header in order to fit all of your topics in.

WARNING - YOU MUST NEVER REORDER THE TOPICS= KEYWORD(S)!

LISTSERV remembers which topics users have selected through their ordering in the "Topics=" keyword. That is, in the example above, "News" is "topic number 1" for LISTSERV, "Benchmarks" is "topic number 2", and so on. This means you can change the name of a topic without requiring users to alter their subscriptions (for instance, you could decide that "Tests" is a better name than "Beta-tests" and just make the change). However, you must never change the order of the topics in the "Topics=" keyword. If you want to remove a topic, replace it with a comma. For instance, to remove the "Meetings" topic, you would change the keyword to:

* Topics= News,Benchmarks,,Beta-tests

Topic names can contain any character except space, colon and comma; the use of double quotes or equal signs is discouraged, as they require special attention when coding list header keywords. In addition, topic names may not start with a plus or minus sign, and the words ALL, NONE, RE, OTHER and OTHERS are reserved.

Posters label their messages through the subject field. LISTSERV first skips any possible sequence of 'Re:' keywords, and takes anything to the left of a colon as a list of topics, separated by commas. The posting is considered to belong to all the topics listed before the colon. If none of these topics is valid for the list, it is classified in a special topic, "Other". If some of the topics are valid but others are undefined, the invalid ones are ignored. At any rate the subject field is left unchanged. Here is an example:

Subject: Benchmarks,News: Benchmarks for XYZ now available!

Messages which should be read by everyone can be posted to the special topic "All". Topic names can be shortened to any unambiguous abbreviation. In our example, "Be" is ambiguous because it could be either "Beta-tests" or "Benchmarks", but "Bench" is acceptable. 

Subscribers select the topics they wish to receive with the SET command. The syntax is 'SET listname TOPICS: xxx' where 'xxx' can be: 

      • A list of all the topics the user wishes to receive. In that case these topics replace any other topics the user may have subscribed to before. For instance, after 'SET XYZ-L TOPICS: NEWS BENCH', the user will receive news and benchmarks, and nothing else.
      • Updates to the list of topics the user currently receives. A plus sign indicates a topic that should be added, a minus sign requests the removal of a topic. For instance, 'SET XYZ-L TOPICS: +NEWS -BENCH' adds news and removes benchmarks. If a topic name is given without a + or - sign, + is assumed: 'SET XYZ-L TOPICS: +NEWS BENCH' adds news and benchmarks. The first topic name must have the plus sign to show that this is an addition, and not a replacement.
      • A combination of the above, mostly useful to enable all but a few topics: 'SET XYZ-L TOPICS: ALL -MEETINGS'.

The colon after the keyword TOPICS: is optional, and TOPICS= is also accepted. Do not forget to include the special OTHER topic if you want to receive general discussions which were not labeled properly. On the other hand, if you only want to receive properly labeled messages you should not include it. ALL does include OTHER.

Finally, it is important to note that topics are active only when your subscription is set to MAIL. Digests and indexes always contain all the postings that were made, because the same digest is prepared and sent to all the subscribers. 

(See also Default-Topics.)