viewing outgoing dns requests

I have a workstation that is connecting to an imap server somewhere on the internet. If I do an nslookup of the imap server it tells me the host is not found. Either there is an alias being used behind the scene or the server is being called explicitly by ip address. I would like to see the lookup/connection on my gateway. The gateway is masquerading the internal network and I would like to know if there is a utility I can run on the console which will show me every lookup or ip address it is contacting for pc's on the internal lan? John