Send Connector
Send connector represents a logical gateway through which outbound messages are sent.
When you configure a Send connector, you must select at least one source server for that Send connector. The source servers are the transport servers that are associated with that connector to handle message delivery.
Transport Servers handle message delivery.
The source server for a Send connector can be a Hub Transport server, an Edge Transport server, an Edge Subscription, or an Exchange Server 2003 or Exchange 2000 Server bridgehead server.
AA,BB,CC, and DD host Hub Transport Role. Send Connector is defined with address space: *.com. AA and BB hub transport servers are associated with the send connector. CC and BB hub transport servers are not associated with it.
Userbox Jane@itsme.com is hosted at AA mailbox server. When Jane@itsme.com sends mail to kkk@yahoo.com. Because the AA transport role coexists with jane's mailbox role, AA transport server always handles the message delivery unless it is unavailable. If AA transport role is not available, BB transport server delivers the message. --Fault tolerance
CC and DD hub transport servers cohost their mailbox roles. When mailbox users on CC send messages to kkk@yahoo.com,aaa@hotmail.com, ddd@cnn.com, etc, the CC hub transport server forwards them to the hub transport servers associated with the send connector. AA and BB can load balanced the message delivery. The AA and BB must be in the same site to load balanced.
Both AA and BB hub transport servers must have direct Internet connections and can resolve the MX records of the Internet domains.
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With the same Exchange Organization, you don't manually create the send connector. When messages from Site A will be relayed to Site B, the Site A hub transport server will contact the hub transport server in Site B.
Each site must have at least one Hub Transport Server.
Message Relay from Hub Transport Server to an Edge Transport server
Mailbox users from Site B send message out to Internet. Hub Transport server in Site B routes them to Site A. The Hub Transport server in Site A relays them to Edge Transport server, which uses DNS name resolution (MX). If there are more than two edge transport servers as the source transport servers on the send connector, load balancing and fault tolerance can happen.
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Send connector and source transport server
If you configure a send connector with name space:* and its source transport server includes one from Site A, one from Site B, and one from Site C, local transport server will always handle the mail delivery for mailbox users in its site. For example, when tom@siteA sends messages to Internet, the messages will be delivered by the Transport Server in Site A.
However, if the source transport server of the Send Connector does not include the Transport server in SITE C, when Joe@SITEC sends messages to Internet, the messages will be relayed to either SITE A or B for delivery, not both. The least cost site link path will be chosen.
