Email list owners are responsible for managing the membership, dealing with delivery errors, and controlling the content of an email list. Generally the creator of an email list is the "primary" owner, but co-owners and ownership transfers are not uncommon. If you are not sure of which lists you are an owner, or you are not sure which of your email addresses is an owner of which lists, you can search for your email address(es) among the ownership of all the listserv.unl.edu lists.
As a owner of an email list you can alter the list's subscriptions and settings with the Owner's Dashboard. You will have to login to see and control your lists' subscriptions and settings. If you haven't yet registered your email address for the listserv.unl.edu web interface, you might want to read the sign-up instructions. Of particular importance on the Dashboard is the "Subscriber Management" function (menu: "List Management" -> "Subscriber Management"). Another useful function is the "List Configuration Wizard" (menu: "List Management" -> "List Configuration" -> "List Configuration Wizard").
If you are receiving stale delivery failure reports for problems you already fixed (or for problems you wish to ignore), you can Clear the delivery error report.