PHP alternative to google groups/ community software

Hi,

we are looking to set up our own little specialist community and wondering if there is a way to have google/yahoo groups type functionality within our own system- Some people have objections to their usage being tracked by google.

Does anyone know anything that could achieve this? OR recommend some other community software.

We really need ‘searchable’ discussions that you can contribute to just by emailing. Membership so only those who have signed up can contribute and the ability to upload and share files but from some kind of manageable repository because as time goes on the resources should increase.

Anyone any ideas, maybe there is some PHP community platform that does this kind fo stuff?

Cheers,

P