Mapping a Network Drive from Branch office

I am trying to map a drive to an image server in our network from the branch office. I have no problem mapping to our DOMAIN server that has an applications folder. When I select “tools” “map drive” select the drive letter and then choose the PC I want the drive from it won’t display the drive. I am baffled. The branch office connect to our main office through a T1 line and has no direct internet access. Any help would be appreciated.