You will notice that this address is not the same email address you used to subscribe to the list. This posting address is referred to as the mailing address. It is used only to post messages. Refer to that saved welcome message and you'll find directions. Lists can be moderated or unmoderated .
Unmoderated lists are the most common.
These are completely automated and maintained by a computer that posts the messages people send and also responds to administrative requests like subscribing and unsubscribing to the list. Sending a personal message to the computer serving as an administrator will not get you a response from a real person. In contrast, moderated lists do have a human being administering them. This is a time consuming job since reading all the messages list members post and making decisions regarding whether or not to forward the messages to the entire list can take many hours of dedicated service. Most list owners or sponsors cannot devote the time to micromanage a discussion list so most lists are unmoderated.