313 & 313-digest are private mailing lists maintained under the EZMLM listserver. To participate you need to first subscribe.
To subscribe you need to send email to firstname.lastname@example.org or email@example.com . This email is simple in format, there doesn't need to be a subject nor a message body. In response to your initial email EZMLM will reply with two emails, the first automated response gives you generic instructions to follow in order to complete the subscription process (usually titled "confirm subscribe to ..."). The second (usually entitled "WELCOME to ...") confirms your subscription request. This is done in two steps in order to prevent someone else from subscribing you to a mailing list without your knowledge and/or approval.
If you don't receive both of these automated responses then there is a definite problem with your email account and I'm afraid there is little that I can do to help you.