They remain a vast, largely untapped resource for those researching virtually any topic. A mailing list is an ongoing discussion focused on a particular topic in which participants converse via e-mail. As long as you can send and receive e-mail, no special software is required. Some mailing lists are automated. Some are moderated.
Participants can subscribe and unsubscribe from lists.
Not all are open to the public. There are upwards of 80,000 mailing lists, so virtually any topic is covered. A moderated mailing list is the best way to have a conversation or trade information with others interested in a common topic. A moderator can decide who's allowed on the list and can ban those who abuse the rules. For that reason, foul language and other inappropriate behavior, such as posting off-topic messages, tend to occur less often.