By default, mail routing fails over for the last hop of the delivery route only. That is, it fails over for the hop to the user's mail server, if the user's mail server is in a cluster. You can configure mail routing to fail over on any hop in the delivery route, or you can disable mail routing failover altogether.

When you configure mail routing to fail over on any hop, if any server along the route is unavailable but is in a cluster, mail routing fails over to a cluster server and that server continues routing the message. Enabling mail routing failover to occur on any hop is particularly helpful if you are using a hub server to route mail. If that hub server is unavailable but is in a cluster, the router delivers the mail to another hub server in the cluster. That hub server continues to send the message toward its destination.

For information about connection topologies for mail routing, see the topic Connection topologies for mail routing.

In the following figure, Mail Server 1 is sending a message to Mail Server 2. It attempts to route through Hub 1, which is the expected route to Mail Server 2. Hub 1 is unavailable, however. Because Hub 1 is in a cluster, IBM® Lotus® Domino™ routes the message to Hub 2, which routes the message to Mail Server 2.

Changing the mail routing failover setting

To change the default mail routing failover setting, make the following change in the Configuration Settings document for every server in the cluster and every server in the domain that can route mail.

1. From the Domino Administrator or the Web Administrator, click the Configuration tab.

2. In the Task pane, expand Messaging.

3. Click Configurations.

4. Do one of the following:

• From the Domino Administrator, select the Configuration document for the server or server group you want, and click Edit Configuration.
• From the Web Administrator, open the Configuration document for the server or server group you want, and click Edit Server Configuration.
If you do not have a Configuration document for the server or server group you want, create one by clicking Add Configuration.

6. In the Cluster failover field, choose one of the following:

• Disabled
• Enabled for last hop only (the default)
• Enabled for all transfers in this domain

Note This setting affects delivery to a client but does not affect sending a message from a client when the mail server is unavailable. If a user sends a message when the mail server is unavailable, the delivery fails over to another server in the cluster, and the router on that server sends the message.

Using shared mail in a cluster

When you send a message to multiple users on a server that is using shared mail, Domino places the header of the message into the recipients' mail databases and places the body of the message into the shared mail database on the server. Before replicating the message to another cluster server, the Cluster Replicator reassembles the message. The server that receives the reassembled message determines if shared mail is being used on that server and if the recipient's mail database is set to always use shared mail. If shared mail is being used, the server deposits the header of the message into the replica of the recipient's mail database and deposits the body of the message into the shared mail database. If shared mail is not being used, the server deposits the entire message into the replica of the recipient’s mail database.

To set up shared mail in a cluster and have replicated messages stored in the shared mail database, you use the same procedure you use for setting up shared mail with replicas that are not in a cluster. This procedure includes the Load Object Set - Always command. You do this on every server that uses shared mail in the cluster.

Glossary