Supporting Multiple Internet Domains

To support multiple Internet domains on a single messaging system, the domains must resolve to your SMTP server's IP address and you must configure the messaging system to recognize the domains.

Configuring domains to resolve to your SMTP server's IP address is a DNS issue. Essentially, the domain's MX record must resolve to the SMTP server's host name and the host name must resolve to the server's IP address.

On the messaging system level, configuring Novell^® NetMail^® to recognize multiple domains is an SMTP Agent issue. All Internet messages enter and leave the messaging system via the SMTP Agent. Because it is the "connection point" with the Internet, the SMTP Agent manages the messaging system's Internet domains. You must add all domains and host names that resolve to the SMTP server's IP address to the SMTP Agent's list of Global or Hosting Domains or its associated Parent objects' lists of Global or Hosting Domains before users can actually receive messages addressed to those domains.

When the SMTP Agent receives a message over the Internet, it looks at the domain portion of the recipient's e-mail address (everything after the @ symbol). If the addressed domain is one of the SMTP Agent's Global or Hosting Domains, the message is placed in the message queue. If the SMTP Agent does not recognize the addressed domain, the message is relayed.

NOTE:  The SMTP Agent does not relay the message if the number of recipients exceeds the Maximum Number of Recipients per E-Mail option configured in the SMTP Agent's UBE Relaying page.

You might compromise the functionality of your messaging server if all domains and host names that resolve to the server's IP address are not added to the list of Global or Hosting Domains in the SMTP Agent or its associated Parent objects. Messages addressed to the overlooked domains are relayed to the domain's address, which actually resolves back to the messaging server. So, the server ends up relaying messages to itself in an endless loop that eventually results in 100% server utilization. The only instance in which the SMTP Agent does not relay messages to itself is if the domain resolves to the server's default IP address or the loopback IP address.

Each domain you add is either serviced by a Global Domain or a Hosting Domain. When adding a domain, determine the domain type to service your domain. Although you can have both Global and Hosting Domains in the SMTP Agent or Parent object configuration, you cannot add a single domain to both lists.

The following sections, Global Domains and Hosting Domains, offer a basic explanation of the SMTP Agent's domain options and how to use them.

NOTE:  For complete information on creating and configuring the SMTP Agent, see SMTP Agent. For more information on defining Global and Hosting domains in the Parent object, see Configuring Parent Objects.

Global Domains

When the SMTP Agent receives a message addressed to a Global Domain, it removes the domain portion of the e-mail address and sends the message to the queue for processing.

The basic process is as follows:

Because Global Domains are not part of the username, you can address users serviced by Global Domains at any of the SMTP Agent Global Domains. For example, messages addressed to johnd@company.com and johnd@company.edu are delivered to the same mailbox if company.com and company.edu are both Global Domains.

Global Domain usernames require unique names. You cannot have one Global Domain user addressed as johnd@company.com and another addressed as johnd@sales.company.com.

Global Domains are most practical in corporate rather than ISP/ASP environments. First, it is more likely that usernames are unique in corporate environments than in ISP/ASP environments. Secondly, ISPs and ASPs typically host domains for unrelated organizations and the users within those organizations are associated with a specific domain. A corporation, on the other hand, can have multiple domains, but it is still a single organization. Therefore, you can address users at any of the organization's domains. Using Global Domains ensures messages are still delivered to the correct user, regardless of the addressed domain.

For the SMTP Agent to recognize Global Domains, you must include them in either the SMTP Agent's or the Parent object's Global Domains lists.

NOTE:  If the Global Domain is listed under the Parent object, you must include the Parent object in the SMTP Agent's list of Parent Objects.

The SMTP Agent's Global Domain

In creating the SMTP Agent, you must define the agent's Global Domain. The Global Domain is the Internet domain you use to identify the messaging system. By default, the SMTP Agent's Global Domain coincides with the messaging server's Official Domain.

Container Domains

Use Container Domains in conjunction with Global Domains; that is, if a Container Domain is defined, include it in the Global Domains list for the SMTP Agent or Parent object.

The Address Book Agent in returning users' address book information or in determining the address book contexts a user can access can reference container Domains. See Address Book Agent for more information.

The Modular Web Agent can also use Container Domains to generate users' Internet e-mail addresses. See User E-Mail Addresses for more information.

IMPORTANT:  Container Domains do not allow you to have non-unique user IDs in different containers.

For complete information on NetMail properties for Container objects, see Container Objects.

Hosting Domains

When the SMTP Agent receives a message addressed to a Hosting Domain, it sends the message directly to the queue for processing; the entire e-mail address remains intact.

The basic process is as follows:

When the NMAP Agent is able to associate the e-mail address with a specific user, it can deliver a message. In other words, the User object's name must match the user's e-mail address. Therefore, users serviced by Hosting Domains must have usernames that are a combination of their name and the Hosting Domain (name@hosteddomain).

Because Hosting Domains are part of the username, you can have duplicate names in the messaging system. For example, annc@hosteddomain.com and annc@hosteddomain.org each resolve to different users. See Managing Duplicate Names for detailed information.

Hosting Domains are most practical in ISP/ASP environments. Using Hosting Domains enables the ISP or ASP to manage duplicate names and associate users with specific domains.

For the SMTP Agent to recognize Global Domains, you must include them in either the SMTP Agent's or the Parent object's Global Domains lists.

NOTE:  If the Hosting Domain is listed under the Parent object, you must include the Parent object in the SMTP Agent's list of Parent Objects.