A mailing list is a collection of names and addresses used by an individual or an organization to send material to multiple recipients. The term is often extended to include the people subscribed to such a list, so the group of subscribers are referred to as "the mailing list", or simply "the list".
At least two quite different types of mailing lists can be defined: the first one is closer to the literal sense, consisting of postal addresses for newsletters, periodicals or advertising. With the rise of e-mail, the "electronic mailing list" or "email list" became popular.
When similar or identical material is sent out to all subscribers on a mailing-list, it is often referred to as a mailshot.
Mailing lists are often rented or sold. If rented, the renter agrees to use the mailing list for only the agreed upon times. The mailing list owner typically enforces this by seeding the mailing list with fake addresses and creates new salts for each time the list is rented. Unscrupulous renters may attempt to bypass salts by renting several lists and merging the lists to find the common, valid addresses. Mailing list brokers exist to help organizations rent their lists. For some organizations such as specialized niche publications or charitable groups, their client list may be one of their most valuable assets and mailing list brokers help them maximize the value of their lists.
Parts of the above definition come from Wikipedia and are subject to the GNU Free Documentation Licence.