Configuring Message Routing

Configure SMTP Advanced Options

In addition to the standard SMTP specification, there is an update called Extension to SMTP (ESMTP). Not all mail servers are capable of using ESMTP, but it is becoming increasingly common. The SMTP sender starts a session by issuing one of two start commands, HELO for SMTP and EHLO for ESMTP. The type of start command determines whether SMTP or ESMTP is used for the session. Because some servers cannot use ESMTP, you can configure Exchange to send the HELO command to specified domains through the SMTP connector.

To save money, many small companies maintain transient connections to their service providers. In addition, sometimes the client (the SMTP sender) depends on mail arriving quickly. Forcing the queues on the server belonging to the client's service provider can be more desirable than waiting for a timeout to occur and the connection to be retried. The TURN and ETRN commands allow the client to request that a remote server start processing its mail queues for messages to the client that are waiting at the server. If there are messages for the client at the server, the server sends the messages at that time.

If you choose to request remote servers to dequeue mail, messages sent to a client through the client's service provider are held until a TURN or ETRN command is received. The ETRN command is more secure than the TURN command because it requests that the server start a new connection aimed at the specified client. Thus, the server is more likely to communicate with the correct SMTP client.

To configure SMTP advanced options:

  1. Start System Manager
    On the Start menu, point to Programs, point to Microsoft Exchange, and then click System Manager.
  2. Navigate to Connectors.
    If you do not have routing groups defined:

    System Manager

    1. Administrative Groups
    2. <Administrative Group>
    3. Connectors

    If you do have routing groups defined:

    System Manager

    1. Administrative Groups
    2. <Administrative Group>
    3. Routing Groups
    4. <Routing Group>
    5. Connectors
  3. Right-click an SMTP connector, click Properties, and then click the Advanced tab.
  4. To send the HELO start message, and use standard SMTP and not extended SMTP, select Send HELO instead of EHLO.
  5. To configure outbound security, click Outbound Security, and then select the appropriate parameters.
  6. To prevent requests on the SMTP connector for remote servers to process the mail in their queues, select Do not send ETRN/TURN. This option is the default.
  7. To specify that dequeing requests are sent with the message, select Request ETRN/TURN when sending messages. If you choose this option, you can also request dequeuing at certain times by selecting the Additionally request mail at specified times check box, and then choosing dequeuing times under Connection time.
  8. To request dequeuing from a server other than the one to which the message is sent, select Request ETRN/TURN from different server, and then, under Server, type the server name.
  9. If you have not disabled dequeuing, to request dequeuing at certain times, under Connection Time, select one of the standard values in the drop-down list, or click Customize, and then select the appropriate connection times on the timetable grid.
  10. To specify the ETRN or TURN command for dequeuing, under Specify how to request that remote servers dequeue mail, select Issue ETRN or Issue TURN. To specify the domains for which the ETRN command should be issued, under Issue ETRN, click Domains, and then add the domains.

Related Topics

Configure SMTP Outbound Security