Troubleshooting Domain Trusts

[Nemesis36]

My company has a WAN in which we have one server in the UK and the other one at my office in the US. Both these servers were synced to each other with firewalls in front and exchangeservers for each location. The UK exchange server would forward on mail to my office's exchange server and everyone on my LAN used the local server for mail. Ok now here is the problem: Recently my DSL company went out of business and I had to get another service, change the static IP on my new router, firewall and server. All of that works great, but now there is a problem when we tried to link the two exchange servers back up, inbound mail is no good. Someone mentioned to us that there may be a problem with the Domain Trust relationship because of the change in IP addresses. Does anyone know what needs to be checked on the exchange servers for both sides to get things back to sync. My co-administrator in the UK has checked everything that he can think of including the routing tables and LHHOSTS file. Any help is already appreciated.