Before joining an email list one should understand what they are. A list is created when a number of people want to talk about a common subject. It is similar to a newsgroup but different in that there is usually a single person who is a moderator. Unlike newsgroups if a message is abusive, off topic or advertising, then the moderator would usually stop it being sent to other members on the list. The main down side of lists is that the people on the list receive messages from everyone else via email.
Some lists can result in subscribers getting a hundred, or more, emails a day.
Even if one only gets a dozen messages a day it doesn't take long for them to mount up. Well, knowing what you are doing is a good help. Ideally you would know this before subscribing, but if not you should be advised on this when your subscription is acknowledged. Be sure to keep this unsubscribe information where you can find it easily. The Datre Net web site.