[Mailman-Users] MailMan For LAN Only

I am wanting to implement MailMan for my company LAN. I am currently running my email server on Postfix. I am wondering if someone can answer these questions for me. If I install MailMan / Apache on my mail server, will the MailMan list be visible by anyone on the web who can access my mail server via Apache? I am worried about spammers using MailMan to harvest valid email addresses. Even though it appears from the reading I have done that non-members can't send to the list w/o moderator approval, I still don't want the vulnerability of exposing my subscribed members email addresses. Can someone please tell me if this is possible and or how I should consider configuring MailMan for my LAN?

Thanks for any assistance!

-- Carlos