Mailing lists may be open to anyone or access may be restricted, depending on the choice of the host or sponsor of the list. Using mailing lists requires no special software, other than your e-mail program. Using e-mail lists broadens your contact with other professionals in your field, with no limits by geographic boundaries. Of course, no assurances can be made about the quality of information provided in a discussion list, but it may be a starting place for your information gathering. Also, what you get out of a list often is related to what you put into it.
Some people avoid discussion lists because they are concerned about receiving too much e-mail.
The amount of e-mail being distributed over a list varies greatly from list to list, depending on the number of subscribers and how often they post messages. Join one list at a time. You can almost always unsubscribe from a list if you start receiving more e-mail than you would like. Most lists send instructions on how to unsubscribe with an initial welcoming message. So, it is best to keep the first message you receive from the list host.