Can you Pass Protect a Lotus Notes Mail List

[ITSFAHYS]

I am trying to find out if a Mailing List on Lotus Notes
can be Password Protected. Running Notes 5.07a
The mail list is available to All Users on the Company
Address Book, and we want to restrict who can send mails to
the Mail List. Under Domino Admin it is setup as a
Multi Purpose Group. I cant see any options for password
protecting the group.

Any Suggestions appreciated,

Stephen.