"DNS suffixes" are used for resolving unqualified domain names (names with no dots).
In the Windows Control Panel, double-click the "Network" icon:
In the "Network" dialog, select TCP/IP for one of your network connections and click the "Properties" button:
In the "TCP/IP Properties" dialog, select the "DNS Configuration" tab, and add your DNS suffixes under "Domain Suffix Search Order":
For more information, please see the following knowledge base article: