XFOR: Cannot Restrict Access by Domain Name if DNS Is Not Configured Correctly

When you use a domain name to restrict access to an IMAP or POP3 virtual server, you need a pointer (PTR) record for that domain in Domain Name System (DNS). Otherwise, the restriction does not work because Exchange 2000 cannot perform a DNS reverse lookup successfully to obtain the fully qualified domain name (FQDN).

The PTR record is a resource record that is used in a reverse lookup zone that is created within the in-addr.arpa domain to designate a reverse mapping of a host IP address to a host DNS domain name.

To add a pointer (PTR) resource record to a reverse zone:

1. Click Start, point to Programs, point to Administrative Tools, and then click DNS.
2. In the console tree, click the applicable reverse lookup zone.
3. On the Action menu, click New Pointer.
4. In the Host IP number text box, type the host IP address octet number.
5. In the Host name text box, type the fully qualified domain name for the DNS host computer for which this pointer record is to be used to provide reverse lookup (address-to-name resolution).
   
   As an option, you can click Browse to search the DNS namespace for hosts in this domain that have host (A) records already defined.
6. Click OK to add the new record to the zone.