threading list archives

[Morna . Findlay @ newcastle . ac . uk (Morna Findlay)]

I'd be interested to know which programs *large* list-server sites use
to mark-up,thread and index their archives for reading on the web.

We have about 1500 lists with about 100K members and have been using
hypermail for a couple of years. We've looked at mhonarc, but think it will
be too slow for us to use.

We (Mailbase) update each list archive every night, but we'd like to move
to doing this dynamically if possible.

Has anyone any similar requirements?

cheers

M