MAIL
If the local Internet domain includes mail systems other than IBM® Lotus® Domino®, users who have Internet addresses ending in yourdomain.com may not have mail files on a Domino server or Person documents in the Domino Directory. When Domino receives a message for such a user, the Router cannot resolve the address. To prevent Domino from generating delivery failures, set up the Domino server to forward mail it receives for unknown local domain users to a local smart host. A smart host is typically a more central computer that has an authoritative directory of all users in the local domain. When Domino receives mail it doesn't know how to deliver, it sends it to the smart host.
In this example, Acme has three Domino servers (Mail1, Mail2, and Mail3) and a third-party SMTP host, smarthost.acme.com, that houses the directory for users who have non-Domino mail files within the acme.com domain. Users in the non-Domino system do not have Person documents in the Domino Directory. The Domino servers have the field "SMTP allowed within the local Internet domain" enabled and have smarthost.acme.com listed in the "Local Internet domain smart host" field on the Router/SMTP-Basic tab of the Configuration Settings document.
If a user on one of the Domino mail servers sends a message to a user in the acme.com Internet domain, and the Router cannot find the recipient in the Domino Directory, the Router forwards that message to smarthost.acme.com over SMTP.
Configuring these servers requires: