ezmlm can also add a “prefix” to the subject line of each message that does not already contain it. This was common on old lists, when mail readers were unable to sort mail, except by subject. It is still popular for historical reasons, even though it violates mail standards. Use this only if you feel that it is necessary, and for novice users where “look” is more important than correctness. If you do use this make it the list name and short, e.g. ‘[mailinglist]’ (well, that's from the example, in real life this is too long and too long a name for a mailinglist as well. ‘email@example.com’ with ‘ml’ would be better). The prefix with the list name can be configured with the ezmlm-make(1) ‘-f’ switch. Alternatively, just place the text in the file DIR/prefix.
For a real thrill, you can use ‘[ml-#]’. Here, ‘#’ will be replaced by the message number, labelling all messages with the message number of the first message in the thread. This is not only a mail standard violation, but will inconvenience many users and html archiving programs. Still, it may be useful and help novice users use the archive efficiently (mail ‘firstname.lastname@example.org’) where ‘#’ is the number in the prefix of the message to get the entire thread from the archive). This works also with partially rfc2047-encoded subjects. (See the ezmlm-send(1) man page for more info.) For a better way to point the recipients to the thread retrieval function see Adding a Trailer.