Using SMTP Connectors

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Updated : September 4, 2001

from Chapter 12, Microsoft Exchange 2000 Administrator's Pocket Consultant by William R. Stanek.

SMTP connectors are another type of Exchange connector. SMTP connectors transfer messages from local bridgehead servers to remote servers. You use SMTP connectors to connect Exchange servers, non-Exchange servers, routing groups, and organizations.

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Understanding SMTP Connectors

Understanding SMTP Connectors

SMTP connectors are a bit more complex than routing group connectors, but the additional settings they make available gives them definite advantages over routing group connectors. With SMTP connectors, you can encrypt message traffic sent over the link and require stricter authentication than with routing group connectors. You can transmit messages to a designated server—called a smart host, which then transfers the message—or you can use Domain Name System (DNS) mail exchanger (MX) records to route messages. If the other mail system supports Extension to SMTP (ESMTP), you can enable extended options as well.

When you install an SMTP connector, you must define which local bridgehead servers the connector will use as well as the connector scope, message routing technique, and address space. SMTP virtual servers act as local bridgehead servers for SMTP connectors. This means that the virtual servers are responsible for routing the message traffic. Multiple local bridgeheads provide load balancing and fault tolerance, which is essential when high availability is a concern. A single bridgehead, on the other hand, ensures that all mail flows through a designated server, but it doesn't provide redundancy.

SMTP connectors have a specific scope that controls how the connector routes messages. You use an SMTP connector with a routing group scope to transfer messages within your organization. You can use an SMTP connector with an organizational scope to connect independent Exchange organizations, to connect Exchange servers with other SMTP-compatible servers (such as Unix Sendmail servers), and to connect Exchange 2000 Server with earlier versions of Exchange Server.

SMTP connectors use smart hosts or DNS MX records to route mail. If you use a smart host, Exchange 2000 Server transfers messages directly to the smart host, which then sends out messages over an established link. The smart host allows you to route messages on a per domain basis. If you use DNS MX records, Exchange 2000 Server performs a DNS lookup for each address to which the connector sends mail.

When you install an SMTP connector, you must also define the address space for the connector. The address space determines when the connector is used. For example, if you want to connect two domains in the same Exchange organization—dev.microsoft.com and corp.microsoft.com—you could create the SMTP connector in dev.microsoft.com, and then add an SMTP address type for the e-mail domain corp.microsoft.com.

You can define multiple address types for a single SMTP connector. The address types can be any combination of SMTP, X.400, MS Mail, cc:Mail, Lotus Notes, and Lotus GroupWise addresses. These address types can point to different domains. Thus, you could use an SMTP connector to connect dev.microsoft.com with sales.microsoft.com, bizdev.microsoft.com, and eng.microsoft.com. You could also use an SMTP connector to connect two specific routing groups.

For load balancing and high availability, you could configure multiple SMTP connectors to handle the same address space. For example, if a large volume of traffic is routinely sent between corp.microsoft.com and support.microsoft.com, you could install two SMTP connectors to handle the message routing between these domains.

Installing SMTP Connectors

To install an SMTP connector, complete the following steps:

  1. Start System Manager. If administrative groups are enabled, expand the administrative group you want to work with.

  2. If available, expand Routing Groups, and then expand the routing group you want to use as the originator of the connection.

  3. Right-click Connectors, click New, and then choose SMTP Connector. This displays the dialog box shown in Figure 12-5.

  4. In the General tab, type a descriptive name for the connector.

  5. To use a smart host for routing, select Forward All Mail Through This Connector To The Following Smart Host, and then type the fully qualified domain name or IP address of the server through which you'd like to route messages. The SMTP connector then uses this smart host to route messages to the remote server.

    Tip If you use an IP address, be sure to enclose the address in brackets, such as [192.168.12.99]. The brackets tell Exchange Server that the value is an IP address and, as a result, Exchange Server doesn't try to perform a DNS lookup on the value.

    Cc722521.exch1205(en-us,TechNet.10).gif

    Figure 12-5: . Use the Properties dialog box to configure SMTP connectors. SMTP connectors transmit messages to a designated smart host or use DNS mail exchanger records.

    Note: The smart host setting for a connector overrides the smart host setting for the virtual servers that act as bridgeheads for the connector.

  6. To use DNS MX records for routing, select Use DNS To Route Each Address Space On This Connector. The precedence order of MX records determines which servers are used in a particular domain.

  7. You must specify at least one local bridgehead server. Click Add, and then select the SMTP virtual server that you want to use as the local bridgehead server. Repeat this step if you want to use additional bridgehead servers.

  8. Connector Scope is set on the Address Space tab. If you're connecting two Exchange organizations, set the Connector Scope as Entire Organization, click Add in the Address Space tab, and then set the properties for the address space. Be sure to set the cost for the address space. Connector costs range from 1 to 100, with the lowest cost having the highest priority for routing. Repeat for other address types that the connector should handle.

  9. If you're connecting two routing groups, set the Connector Scope as Routing Group, and then click Add in the Address Space tab and set the properties for the address space. Be sure to set the cost for the address space. Connector costs range from 1 to 100, with the lowest cost having the highest priority for routing. Repeat for other address types the connector should handle. Afterward, click Add in the Connected Routing Groups tab, and then select the routing group to which you want to connect.

    Note: You'll usually want to use the SMTP address type when the routing group to which you want to connect contains Exchange servers. With SMTP address types, you can enter an asterisk (*) as the domain to have the connector route messages for all domains in the routing group you're connecting.

  10. If you want to allow the local server to relay messages to domains in the other organization or routing group, select Allow Messages To Be Relayed To These Domains.

  11. Click OK to install the connector. Later, you may want to set delivery options, outbound security, delivery restrictions, content restrictions, and advanced controls.

Configuring Delivery Options for SMTP Connectors

SMTP connectors have delivery options that determine when messages are sent through the connector as well as whether messages are queued for remote delivery. To control when messages are sent, you set connection schedules. You can have separate schedules for standard-sized and large-sized messages. To control message queuing, you can enable or disable message queuing for remote delivery on a per user basis. From then on, when a specified user logs on to the network, Exchange Server triggers delivery of all queued messages for this user, and this way you can more efficiently manage how messages are delivered to remote clients with temporary connections.

You configure delivery options for SMTP connectors by completing the following steps:

  1. In System Manager, navigate to Connectors. Right-click the SMTP connector you want to configure, and then select Properties.

  2. Click the Delivery Options tab, as shown in Figure 12-6. Use the Connection Time list box to specify the times when messages are sent through the connector.

  3. To set separate delivery options for standard and large messages, select Use Different Delivery Times For Oversize Messages. In Oversize Messages Are Greater Than (KB), type the minimum size, in kilobytes, of messages you want to designate as oversized. The default is 2000 KB. Finally, use the options in the second Connection Time list box to set the delivery times for large messages.

  4. Message queuing is ideal for clients who connect periodically to download messages. To enable message queuing for remote users, select Queue Mail For Remote Triggered Delivery. Click Add, and then use the Select Recipient dialog box to specify users who should have this option.

  5. Click OK.

    Cc722521.exch1206(en-us,TechNet.10).gif

    Figure 12-6: . Use the Delivery Options tab of the SMTP Connector Properties dialog box to control when messages are sent through the connector. Note that delivery options for SMTP connectors are slightly different than those of routing group connectors.

Configuring Outbound Security for SMTP Connectors

By default, SMTP connectors don't authenticate connections to remote domains. This means that the connectors anonymously access remote domains to send messages. You can, however, configure an SMTP connector to pass authentication credentials to remote domains. The key reason to do this is that you require a specific level of authentication to access a remote domain or you're sending messages to a specific address in the remote domain that requires authentication.

Exchange 2000 Server supports three types of authentication:

  • Basic Standard authentication with wide compatibility. With basic authentication, the user name and password specified are passed as clear text to the remote domain.

  • Integrated Windows Authentication Secure authentication for Microsoft Windows-compatible domains. With integrated Windows authentication, the user name and password are passed securely to the remote domain.

  • TLS Authentication Encrypted authentication for servers with smart cards or X.509 certificates. Transport Layer Security (TLS) authentication is combined with basic or integrated Windows authentication.

To configure SMTP outbound security, follow these steps:

  1. In System Manager, navigate to Connectors. Right-click the SMTP connector you want to configure, and then select Properties.

  2. Click the Advanced tab, and then click Outbound Security. This displays the dialog box shown in Figure 12-7.

    Cc722521.exch1207(en-us,TechNet.10).gif

    Figure 12-7: . Use the Outbound Security dialog box to set security options on outgoing messages.

  3. If you want to set standard authentication for wide compatibility, select Basic Authentication, and then click Modify. Otherwise, to set secure authentication for Windows-compatible domains, select Integrated Windows Authentication, and then click Modify. The Outbound Connection Credentials dialog box should be displayed.

  4. Use the Account, Password, and Confirm Password fields to set the authentication credentials. Click OK.

  5. If you want to encrypt message traffic and the destination servers in the remote domain support smart cards or X.509 certificates, select the TLS Encryption check box.

    Caution: The destination servers in the remote domain must support smart cards or X.509 certificates. If the servers do not, all messages sent across the connector will be returned with a nondelivery report.

  6. Click OK.

Setting Advanced Controls for SMTP Connectors

Advanced options for SMTP connectors control whether Exchange Server uses standard SMTP or Extension to SMTP (ESMTP) as well as how mail delivery is initiated using SMTP or ESMTP. The key reason for using ESMTP is that the standard is more efficient and secure than SMTP. However, some messaging systems, particularly older ones, don't support ESMTP, and you may need to disable ESMTP support to prevent errors.

By default, SMTP connectors always try to initiate ESMTP sessions, but you can change this behavior using the HELO and EHLO start session commands. SMTP connectors initiate SMTP sessions with other mail servers by issuing the HELO start command. SMTP connectors initiate ESMTP sessions with other mail servers by issuing an EHLO start command.

By default, SMTP connectors don't force delivery of queued messages. Forced delivery is necessary when you queue mail for remote triggered delivery. Not forcing delivery causes delays as clients first wait for a connection timeout, and then have to retry the connection. Two commands control delivery of queued messages. These commands are TURN and ETRN. TURN is a command for SMTP, and ETRN is a command for ESMTP. These commands allow a mail client to ask a remote server to start processing mail queued for delivery to the client.

You can configure these advanced options by completing the following steps:

  1. In System Manager, navigate to Connectors. Right-click the SMTP connector you want to configure, and then select Properties.

  2. Click the Advanced tab. This displays the dialog box shown in Figure 12-8.

  3. The Send HELO Instead Of EHLO check box controls whether SMTP or ESMTP is used. To use SMTP, select this option. To use ESMTP (which is the default), clear this option.

  4. Configure remote triggered delivery of messages using the following options:

    • Do Not Send ETRN/TURN Prevents clients from requesting that remote mail servers start processing queued mail. In the Delivery Options tab, you should ensure that Queue Mail For Remote Triggered Delivery isn't selected.

    • Request ETRN/TURN When Sending Messages Enables remote triggered delivery of messages. If you want to automatically request messages at a specified interval, select Additionally Request Mail At Specified Times, and then set the interval using the Connection Time selection list.

    • Request ETRN/TURN From Different Server Requests that messages are triggered for delivery from a server other than the one to which the messages are sent. If you select this option, you must specify the server name in the Server field. You must also set the interval for message delivery using the Connection Time selection list.

  5. If you enabled remote triggered delivery and requested ETRN/TURN, you must specify how the requests are submitted to remote servers. Select either Issue ETRN or Issue TURN. To specify domains for which ETRN should be used, click Domains, and then add the domains.

  6. Click OK.

    Cc722521.exch1208(en-us,TechNet.10).gif

    Figure 12-8: . Use the Advanced tab of the SMTP Connector Properties dialog box to configure whether the connector should use SMTP or ESMTP.

Performing Other SMTP Connector Tasks

You perform most other SMTP connector tasks in the same way you perform tasks for other connectors. The section of this chapter entitled "Handling Core Connector Administration Tasks" explains these common tasks.

from Microsoft Exchange 2000 Administrator's Pocket Consultant by William R. Stanek. Copyright © 1999 Microsoft Corporation.

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