Network configuration for Mantis

i am running Mantis on Windows XP/32 Professional. The machine has an internal IP address of [login to view URL] and an external address of 99.X.Y.Z (will provide XYZ once i choose a bidder). If i add/update a Mantis issue while within my internal subnet .. the notification from Mantis goes out by email to the developer who sees the internal IP address .. instead of the public IP address. This is a pain since the developer then has to manually update the IP address to the public IP. If however i add/update a Mantis issue while outside my subnet .. (i.e. from the internet accessing Mantis using the public IP address) then notifications from Mantis correctly uses the public IP address I need a solution to this problem so that i can 1) access my public IP from inside my internal subnet and then 2) have Mantis always use the public IP address in the mantis notifications sent out