The List Owner can define up to 11 topics for the list. This could seriously impair the topic capability of your list. Some people predefine all topics, so they will not be tempted to re-order them later. If you want to remove a topic, simply delete the topic word and replace it with a place-holding number. The use of double quotes or equal signs is discouraged, as they require special attention when coding List Header keywords.
Subscribers label their messages through the subject field.
The posting is considered to belong to all the topics listed before the colon. If some of the topics are valid but others are undefined, the invalid ones are ignored. The subject field is left unchanged. Topic names can be shortened to any unambiguous abbreviation. There are three methods by which List Subscribers may be configured to receive topics.