Restrict Access by IP Address, Subnet, and Domain

If you have a small number of clients who do not use the POP3 service, you can deny access to only those clients. By default, all computers can access this resource until you identify a group of restricted IP addresses, subnets, or domains.

Warning   Identify a restricted computer by IP address only if you assign IP addresses statically. If a DHCP server assigns temporary IP addresses to computers, you cannot ensure that a computer will always use the same IP address.

To restrict access by IP address, subnet, and domain:

1. Start System Manager
   on the Start menu, point to Programs, point to Microsoft Exchange, and then click System Manager.
2. Navigate to POP3.

   System Manager

   1. Administrative Groups
   2. Administrative group
   3. Servers
   4. Server
   5. Protocols
   6. POP3
3. In the console tree, right-click a virtual server, and then click Properties.
4. On the Access tab, click Connection.
5. Select Only the list below, and then click Add.
6. Select one of the following options:
   • IP address. Type the static address of a single computer; for example, 192.168.114.201.
   • 
     
     

     Tip   If you know only the name of the computer, click DNS Lookup. Type the name of the computer, and then click OK. If resolved, the IP address appears in IP address automatically.

   • Group of Computers. Type the subnet address and mask; for example, a subnet address of 172.17.131.0 and a subnet, mask of 255.255.250.0
   • .
   • Domain. Type the complete domain name; for example, nwtraders.microsoft.com.
7. Click OK to add the user, subnet, or domain to the list of restricted users.

Note   Restricting a computer's access to one POP3 virtual server does not necessarily restrict access to all instances of POP3 virtual servers. If you do not want a particular computer to access any POP3 service, you must specifically add the computer to each POP3 virtual server instance. If you restrict a computer from accessing only one instance of a POP3 virtual server, depending on how you configure access to the other instances, the computer might still have access to another POP3 virtual server.