Understanding Foreign Connectors

Applies to: Exchange Server 2010

A Foreign connector can only be installed on a computer that's running Microsoft Exchange Server 2010 and that has the Hub Transport server role installed. A Foreign connector uses a Drop directory to send messages to a local messaging server that doesn't use SMTP as its primary transport mechanism.

Overview of Foreign Connectors

Exchange 2010 Hub Transport servers require Foreign connectors to deliver messages to foreign gateway servers that don't use SMTP to transmit messages. Third-party fax gateway servers are examples of foreign gateway servers. A Foreign connector controls outbound connections from the Hub Transport server to the foreign gateway server. The outbound messages are put in a Drop directory on the Hub Transport server or in a network file share on a remote server. Each Foreign connector uses its own Drop directory. The foreign gateway server must be configured to obtain messages from the Drop directory that's specified for that Foreign connector.

Foreign connectors that are created on Hub Transport servers are stored in Active Directory and are available to all Hub Transport servers in the organization. In Active Directory, a Foreign connector is created as an object in the connections container. When a Hub Transport server in the organization routes messages to an address space configured on a Foreign connector, the message is delivered to a source Hub Transport server for that Foreign connector to be relayed to the destination domain. You can specify several different Hub Transport servers in your organization as source servers for a Foreign connector. This provides fault tolerance for the Foreign connector. If a Hub Transport server that contains the Foreign connector is unavailable, the messages that are destined for the Foreign connector's address space are relayed by using any of the other defined and available Hub Transport servers. To provide this fault tolerance, you must make sure that the Drop directory that's specified by the Foreign connector is accessible by all Hub Transport servers that are designated as source servers for that Foreign connector.

Foreign gateway servers can send messages into the Exchange 2010 organization by using the Replay directory that exists on the Hub Transport server. Correctly formatted e-mail message files that you copy to the Replay directory are submitted for delivery.

For more information about the Replay directory, see Understanding the Pickup and Replay Directories.

Defining the Usage of a Foreign Connector by Using Address Spaces and Connector Scope

The address space for a Foreign connector specifies the recipient domains to which the Foreign connector will route e-mail. You can specify SMTP address spaces or non-SMTP address spaces. In Exchange 2010, the complete syntax for specifying an address space is as follows.

<AddressSpaceType>:<AddressSpace>;<AddressSpaceCost>

You can use the scope of a Foreign connector to control the visibility of the Foreign connector within the Exchange organization. By default, all Foreign connectors that you create are usable by all the Hub Transport servers in the Exchange organization. However, you can limit the scope of any Foreign connector so that it's only usable by other Hub Transport servers that exist in the same Active Directory site.

The connector scope is specified by using the IsScopedConnector parameter in the New-ForeignConnector cmdlet or the Set-ForeignConnector cmdlet. When the value of this parameter is $false, the connector can be used by all Hub Transport servers in the Exchange organization. When the value of this parameter is $true, the connector can only be used by Hub Transport servers in the same Active Directory site.

Foreign Connector DSN Handling

When a message is sent with a delivery confirmation request to an address that's serviced by a Foreign connector, the sender should be notified if the recipient's messaging server can't correctly process the delivery confirmation request. A Relayed delivery status notification (DSN) notifies the sender that the recipient's messaging system is unable to forward delivery confirmation requests. By default, Relayed DSN messages aren't generated for messages sent to the address spaces that are serviced by a Foreign connector. DSN messages are defined in RFC 1894. For more information about DSN messages, see Managing Delivery Status Notifications.

Delivery Agent Connectors

Exchange 2010 introduces a new feature called Delivery Agent connector, which is also used to route messages to foreign systems that don't use the SMTP protocol. When a message is routed to a Delivery Agent connector, the associated delivery agent performs the content conversion and message delivery. Delivery Agent connectors allow queue management of Foreign connectors, thereby eliminating the need for storing messages on the file system in a Drop directory. They provide greater control over the message delivery to the foreign systems. To learn more, see Understanding Delivery Agents.