Unoverica Message Transport v2.11 Chapter 5: Configuring Mail Routing

Chapter 5: Configuring Mail Routing

5.3 Scenario 2: Routing Mail Through an External Site

Smaller organizations that cannot justify a full-time Internet connection typically rely on an external site (such as an Internet Service Provider) for Internet mail routing. However, these organizations still want to be able to use domain-based routing, although they may not be able to use the full-time delivery mechanisms described in section 5.2 Scenario 1: Routing Mail for a Domain. Figure 5.17 below illustrates this concept:

Figure 5.17: In this configuration, an external system (such as an ISP's mail server) accepts all in-bound and out-bound mail on behalf of the local system.

There are four steps required before you can use an external site for mail routing services:

Configure your mail server to forward all non-local mail to a "smart" relay host. For more information on how to do this, refer to section 5.3.1 Forwarding All Out-Bound Mail to a Relay Host.
Have the relay site configure their systems so that any in-bound mail waiting to be delivered will be automatically transferred to your site. For more information on this subject, refer to section 5.3.2 Configuring the External Site to Send Waiting Mail.
Configure Unoverica Message Transport to support delivery to the local domain without using DNS. For more information on this subject, refer to section 5.3.3 Adding the Domain to Unoverica Message Transport.
Configure your mail clients and Unoverica Message Transport to mark outbound mail as being from user@domain.com instead of user@host.domain.com. For more information on this subject, refer to section 5.3.4 Changing the From: Headers.

Once these steps have been accomplished, you can use SMTP and POP3 mail for local messaging on your LAN, while also using it to communicate with the world via the Internet.

STEP: To continue to the next step in the configuration process, go to section 5.3.1 Forwarding All Out-Bound Mail to a Relay Host.