You have the following options:
1. As soon as someone contributes a message to the mailing list, the user will receive a copy of that message.
2. Each night, the user will receive a single email message containing all the messages contributed to the mailing list that day in plain-text; all HTML and attachments will be stripped. At the top of the message will be a numbered list of the subjects in that digest, followed by the complete messages themselves. Digest recipients will not receive messages sent to segments.
3. The same as a digest, but in MIME format so that the individual messages' formatting is preserved. Digest recipients will not receive messages sent to segments.
4. Each night, the user will receive a single email message containing all the subject lines of all the messages contributed to the mailing list that day. If any of the messages interest the user, the bottom of the index gives the email command that will retrieve the bodies of the messages.
5. No email is sent to the user. The user is free to go the web interface whenever they want, and read the full text of the messages there. This setting is useful for when members go on vacation and want to stop receiving mail.
To change your preference, go to the List Manager page, log in to your list/forum, click on the tab in the column at the left side of the page labeled "My Account" and go to "Membership type." The drop-down menu there gives you the mail options.