Restrict Access by IP Address, Subnet, or Domain
If you have a small number of clients who do not use the IMAP4 service, you can create a group of restricted computers that cannot access the IMAP4 virtual server. Limiting access to server resources enhances security and can improve performance by reducing the load on a server. By default, all computers can access the IMAP4 virtual server 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 a computer will always use the same IP address.
To restrict access by IP address, subnet, or domain:
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.
Note Restricting a computer's access to one IMAP4 virtual server does not necessarily restrict access to all instances of IMAP4 virtual servers. You must restrict the computer's access to each IMAP4 virtual server if you do not want that computer to access any IMAP4 service. Otherwise, if you restrict a computer from accessing only one instance of an IMAP4 virtual server, depending on how you configure access to the other instances, the computer might still have access to another IMAP4 virtual server.