Callout Schedule Not Affected by Message Priority

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Each X.400 connector or site connector in Exchange Server has its own schedule, which defines the specific times and blocks of time when the Exchange Server MTA can initiate connections to the other Exchange Server MTA or foreign mail system. This schedule can be set from the X.400 Connector's or Site Connector's Schedule property page from the Microsoft Exchange Administrator program.

Whenever a message is handed over to the Exchange Server MTA, the MTA decides, based on the routing information, which X.400 connector or site connector to use to send the message. Once a connector is identified by the Exchange Server MTA, the MTA moves the message into that connector's queue. If the message is high priority, it is placed at the top of the queue for that connector.

The Exchange Server MTA cannot initiate a connection on the connector until the connector's schedule permits it to do so. This means that all messages (with either high or low priority) will sit in the queue until the X.400 connector or site connector is scheduled to connect and transfer messages.

Example

A site called DALLAS has the following connectors to three other sites:

• X.400 connector to New York on X.25 transport stack is scheduled to connect only between 11:00 P.M. and 5:00 A.M.
• Site connector to Seattle is scheduled to connect always.
• X.400 connector to Houston on Remote Access Services (RAS) transport stack is scheduled to connect only between 8:00 P.M. to 8:00 A.M.

If a user at site Dallas sends a high-priority message to users in New York, Seattle, and Houston at 10:00 A.M., the message is transferred at the following times:

• The message is put at the top of the work queue for the X.400 connector to New York because it is a high-priority message. The X.400 connector to New York will connect at 11:00 P.M. and will then move the message to New York.
• Because the site connector to Seattle is scheduled to connect always, the message is moved as soon as the Exchange Server MTA hands the message to this connector.
• The message is put at the top of the work queue for the X.400 connector to Houston because it is a high-priority message. The X.400 connector to Houston will initiate a call at 8:00 P.M. and then move the message to Houston.