Mojo Mail Free script that you will need to install in a CGI bin.
a. automatic subscribes (by an email address) — yes
b. automatic unsubscribe (by an email address) — yes
c. automatic removal of undeliverables or error mails — no
d. archives — yes
e. mailloops (autoresponder messages) — yes
f. security features — yes
This is a great little program. If you are handy at installing scripts, I highly recommend you give this program a try. It has everything you will need except the handling of undeliverables.