The Domino Directory and mail routing

The Domino® Directory (names.nsf) is the most important database on a server. It defines the primary administrative unit in a Domino network, the Domino domain, which is a group of servers that have the same Domino Directory. The Domino Directory serves as the control center for the domain. Administrators use it to manage users and connect and configure servers and it contains almost all of the essential information required for routing mail.

When you set up the first IBM® Domino server, the setup program creates your Domino domain's Domino Directory. Each server in the domain stores a replica of the Domain's Domino Directory. Domino replication synchronizes the Domino Directories on each server.

In addition to the Domino Directory, Domino retrieves information from the server's NOTES.INI file and, when routing mail over SMTP, from the Domain Name System (DNS), which is maintained separately.

The Domino Directory supports LDAP so that Internet mail clients can use LDAP to query and modify the directory if they have access to do so.

For ease of maintenance, when entering server information in the Domino Directory, refer to the server by its fully-qualified host name rather than its IP address. Although Domino fully supports IP addresses, host names are less subject to change than numeric addresses. For example, for TCP/IP to work properly a server's numeric IP address must change if you move the server to a new subnet, or have to merge two networks as the result of reorganization. Using a host name in the same documents, on the other hand, would not require any update.

Domino routing tables

A routing table is a list of connections from a Domino server to all other servers it can contact. Domino uses the routing table to determine the best, least-cost path to deliver mail. When you start the router on a server, it gathers information from the NOTES.INI file, and the Configuration Settings, Connection, Domain, and Server documents in the Domino Directory to build a dynamic routing table.

The router automatically recalculates the routing table after you reboot the server or restart the router task. In addition, the router checks the Domino Directory for changes at intervals of approximately five minutes. If it detects changes in these source documents, it rebuilds the routing table to incorporate the new information.

You can use a TELL command to refresh the routing table without having to restart the router. The ability to update the routing table on demand is especially useful when testing new configuration settings.

How the router uses the Domino Directory to look up mail recipients

When a user sends mail to a recipient in the local domain, the router looks up the complete address in the ($Users) view of the Domino Directory (if you set up Directory Assistance, the router can also look up the address in a secondary directory) for the recipient's Person document, which lists the recipient's home server. If the recipient's home server is the current server, the router will deliver the message. If it is a different server, the router consults the routing table to determine the best route, or least-cost path, for transferring the message to the destination home server and routes the message along that path.

If the router cannot find a match for the recipient in the specified directories, it can forward the message to a "smart host," which is a server that has a directory of users who are in the local domain but who are not listed in the Domino Directory. For example, if you are migrating users from a UNIX™ sendmail system to a Domino mail system but you have not migrated all users yet, you set up a UNIX server as a smart host that can locate the sendmail users and route mail to them. Enter the name of the smart host in the Local Internet domain smart host field on the router/SMTP-Basics tab of the Configuration Settings document.

Documents used for routing mail

The Domino Directory uses numerous documents to define the messaging topology. Depending on your needs, you may need to create or edit the following documents:

Table 1. Routing Document Names and Descriptions
Documents	Description
Server documents	Every Domino server requires a Server document. Server documents specify the following for each server: IBM Notes® name; IP address; fully-qualified Internet hostname; Domino domain; the Notes Named networks it is a member of; Internet messaging ports and services available, such as the IMAP, POP, and SMTP ports; the security options for each port.
Configuration Settings documents	Configuration Settings documents provide additional information that determines how servers process incoming and outgoing mail. They define Router settings for SMTP and Notes routing; set inbound SMTP restrictions; provide MIME conversion information; configure mail access for IMAP, IBM iNotes® clients.
Connection documents	Connection documents define the routing path to servers outside the current Domino domain or Notes Named Network.
Global Domain documents	Global Domain documents identify the Internet domains considered to be internal to a Domino domain and for which the local domain can accept mail. Also provides instructions for converting the sender's Notes mail address to an SMTP address.
Adjacent and Non-adjacent Domain documents	Adjacent and Non-adjacent Domain documents specify the domains from which the current domain will accept mail destined for a specified adjacent or non-adjacent domain. Non-adjacent Domain documents also define the intermediary domain through which the local domain routes mail intended for a Notes domain to which no direct connection exists.
Foreign SMTP Domain documents	Foreign SMTP Domain documents define the relationship between Domino domains and SMTP mail systems.
Internet Site documents	Internet Site documents provide protocol information for IMAP, POP3 and SMTP ports. If configured, the information in a Site document takes precedence over settings for the port in the Server document.
File Identification documents	File Identifications documents define the relationships between the file extensions and MIME types and subtypes of various file types.
Person documents	Person documents provide information about the location of the user's mail file; Notes and Internet mail addresses; Internet passwords required for HTTP, POP3, and IMAP access; and mail storage preferences.