Important information on Sender Restrictions
It is strongly recommended that Sender Restrictions are activated. Doing so will reduce the chances of unintended email distribution or misuse of maillists. Typically, it is best to restrict sending to a specific group of individuals rather than allowing anyone to send to the maillist.
Under the Sender Restrictions tab, leave 'Restricted Sender' activated for both SFU and non-SFU users, uncheck 'Allow SFU members to send', and uncheck 'Allow non-SFU members to send'. You can then specify allowed senders under the 'Allowed Senders' tab.
For more information, please refer to the SFU Maillist Online Help document