Ask YC: best (multi-user) startup email support/helpdesk system?

What's the best email support/helpdesk system to use for our startup that lets more than one person process incoming email?

Currently we have an email alias support@ which simply sends to two of us (web feedback form submissions come this way too). When one of us replies then we BCC the other so they know not to reply too, but this is obviously a pain. Additionally if we reply from our personal address then the other person no longer receives future messages in the thread.

As well as solving these two problems, it'd be useful to bring some more of the team into the process so they at least can read the incoming support requests to get an idea of user feedback - this would quickly get out of hand with our current simple setup.

Any recommendations? Cheers!

There's also a whole list here: http://www.opensourcehelpdesklist.com/

Are you hosting this yourself or do you want someone else to host it?

Not sure if it's the right fit for you, but it's run by some friends of mine.