Server Location Slow Over VPN

When I connect via VPN to my company’s network, I do so without problem in terms of logging in. If I search for a server by name I am able to locate it so DNS is working OK. My problem is that it can take as much as a minute to find a server. In contrast, when I remotely connect to our email server, I can retrieve and open an email message in no more than 20 seconds. Why so long to find a server and how can I improve it?