Issue with Exchange 2007

We have an Exch 2007 Server on-site in our office, along with a separate OWA server for remote emails on phones, laptops at home etc. Today the remote emails suddenly stopped working. Emails are fine on desktops in the office. It's just the remote stuff that doesn't work. My regular go-to guy has just spent 4 hrs trying to sort and no joy. It appears that the Exch server is refusing to connect to the OWA server, but that's as far as we can get.
Need to find a 2007 expert to get us up and running today, as our 3 staff are all working remotely and need emails up asap.