You can add a list subscription link to your webpage that will allow users to subscribe to your list via email commands. The link will open a message in their native mail client that will have the subject and body of the message filled out for subscription to your list.

Before adding the link, you will need to first set your list's subscription to Open, Confirm. To update your settings, in the PennNet Mailing List Service, go to List Configuration>Subscriptions>Subscription and select Open and check the box for Confirm and then select Update.

You can then use the below HTML to generate a subscription link for your list in your web page:

<a href="mailto:listserv@lists.upenn.edu?subject=subscribe&BODY=subscribe SAS-NAME-OF-LIST">Subscribe using Email</a>

replacing SAS-NAME-OF-LIST with the name of the list to which you would like users to subscribe.