Exchange Edge server is deployed on perimeter network. Network is configured as Internet--Hardware firewall (port forward to edge server)--perimeter network (Edge Server)--hardware firewall--internal router--internal network External dns has backup mx configured. What I want to know is in Case of internal router failure. there will be no contact between edge server and and internal network (AD & hub server). Will external email still be received on Edge server. and if yes how long will edge server store them ? what is the no. of mails and days limits in case no internal network connection is restored?

Yes the edge server will hold the inbound mail in its queue database. The queue database does have a limit, but more likely you'll hit the physical disk capacity limit first. Mike Crowley A+, Network+, Security+, MCT, MCSE, MCTS, MCITP: Enterprise Administrator / Messaging AdministratorDo you still have Exchange 2000? Looking to upgrade to Exchange 2010? Read how.

Oh, and for your other timing questions, see the similar post here. Mike Crowley A+, Network+, Security+, MCT, MCSE, MCTS, MCITP: Enterprise Administrator / Messaging Administrator Do you still have Exchange 2000? Looking to upgrade to Exchange 2010? Read how.