If IPCONFIG displays an IP address in the DNS Servers box, the client computer is configured to resolve host names through the DNS.
The next step in troubleshooting is to verify that the DNS server is available. At the command prompt, ping the DNS IP address. If the DNS does not respond to the request, additional attempts are made at 5–, 10–, 15–, and 20–second intervals. This is the design of DNS and is usually the cause of slow client startup.
If the client computer is configured for a DNS server that is not available, then DNS either needs to be disabled or configured for a DNS server that is available at all times.
If the DNS server is available and configured properly, the Microsoft Exchange Server computer name and IP address need to be added to the DNS database. After this is done, pinging the Microsoft Exchange Server computer name will resolve to an IP address by the DNS server, enabling faster startup times of the Microsoft Exchange Client.