Hackers start by learning that an e-mail server exists, which generic scanning tools can tell them. Coupled with the public information of your Domain Name System (DNS) records, hackers can quickly know a lot about your network.
Finding company information is easy for anyone. You can do it. Simply open a command prompt and type nslookup. Set the type of the record you’re looking for to a mail exchanger (MX) record by typing set type=mx. Type a domain name. This example uses Microsoft.com. Figure 19-1 shows the results.
Figure 19-1. Using the NSLookup tool to find the public MX records for Microsoft.com
Next, the hacker determines the ...