Topic Last Modified: 2007-02-01

Use the Computer dialog box to specify the IP addresses or domain names to which you want to grant access or deny access. You can specify a single computer, a group of computers, or a domain name. The following options are available on the Computer dialog box.

Single computer

Select this option to grant access or deny access to a single computer. If you select this setting, the following options are available:

  • IP address   Enter the IP address of a single computer.

  • DNS Lookup   If you know the name of the computer that you want to add to the list, but do not know the IP address, click DNS Lookup. In the dialog box that appears, enter the DNS name of the computer, and then click OK. The DNS server will resolve the computer name to an IP address and SMTP Server will automatically populate the IP address field.

Group of computers

Select this option to grant access or deny access to all the computers within a specific subnet. If you select this option, you must enter the following information:

  • Subnet address   Enter the base IP address for a group of computers.

  • Subnet mask   Enter the subnet mask that specifies the range of IP addresses to which the base IP address extends.

For example, if you enter a subnet address of 192.168.1.0 and a subnet mask of 255.255.255.0, all computers that have an IP address in the range of 192.168.1.1 to 192.168.1.254 are included in the group of computers.

Domain

Select this option to grant access or deny access to all the computers in a specific domain. If you select this option, you must enter the domain name in the Name field. Restricting access by domain name requires a reverse DNS lookup on each connection. The additional processing overhead can affect overall SMTP Server performance.