If a listserv you are subscribed to sends many messages per day, you can view these messages in a single email as a digest. Digest settings can be managed through the Northwestern Listserv Web Interface or by sending an email command.
If you are unsure whether your list is configured for digests, you can check by using the REVIEW command. Send a plain text message to email@example.com with no subject line or email signature and REVIEW listname in the body. In the message that is returned to you, look for the line which begins with DIGEST:.
If the line says no digests collected, then you need to write to the list owners and request that it be turned on. You can reach the list owners by sending an email to firstname.lastname@example.org (where listname is the name of the list you're subscribed to).