Mailman tips

I'm trying to set a list for an association. They only need user
moderation. Their host blocks any msg w/ more than 30 recipients via
SMTP and 2000/day via php mail().

I was thinking of mailman, but it seems impossible as it needs smtp (and
there's about 200 recipients, and growing).

Is there any alternative? Software or (free/really cheap) service (as an
SMTP host).

This is NO spam, no newsletter. Just a discussion group, pretty much as
those on Xaraya. 

Thanks in advance,
Murilo