Connections Properties

Use the Connections property page to configure transfer mode, message delivery, connection acceptance, security, retry interval, and message time-out options for the Internet Mail Service.

Getting to the Connections property page

1. In the Administrator window, choose a site, and then choose Connections.
2. Double-click the Internet Mail Service to be modified.
3. Select the Connections tab.

Specifying Inbound and Outbound Transfer Modes

Use the Connections property page to configure the Internet Mail Service to accept inbound messages, send outbound messages, both, or neither. In an organization using one Internet Mail Service, you set the transfer mode to both send and receive messages. In an organization using multiple Internet Mail Services, you can balance responsibility for sending and receiving messages among the services. Use the None option when you want to suspend further message activity when preparing to remove or move the Internet Mail Service.

Note   Setting the transfer mode to Inbound Only will not prevent outbound messages from being queued to this Internet Mail Service. To prevent outbound messages from being queued to this Internet Mail Service, remove the address spaces from the Address Space property page.

1. Select the Connections tab.
2. Under Transfer Mode, select Inbound & Outbound, Inbound Only, Outbound Only, or None.

Option	Description
Inbound & Outbound	Accept inbound and attempt outbound connections.
Inbound Only	Only accept inbound connections.
Outbound Only	Only attempt outbound connections.
None (Flush Queues)	Do not accept inbound connections. Pending messages are delivered.

Defining the Maximum Number of Connections and Messages Sent

Use the Connections property page to specify the maximum number of inbound and outbound connections the Internet Mail Service will accept and initiate respectively at one time. You can also define the maximum number of messages sent during each connection and adjust the number of connections and messages based on resources available in your environment. Some mail systems can accept only one connection at a time. The maximum number of combined inbound and outbound connections cannot exceed 1,000.

Note   Setting the maximum number of inbound and outbound connections to 0 does not stop the Internet Mail Service from accepting inbound or attempting outbound connections. For more information, see "Specifying Inbound and Outbound Transfer Modes" earlier in this chapter.

If you have a server supporting Post Office Protocol version 3 (POP3) or Internet Message Access Protocol Version 4rev1 (IMAP4) clients, you may need to increase the maximum number of simultaneous SMTP connections. POP3 and IMAP4 clients need to create an SMTP connection to the Internet Mail Service to send mail, but the number of simultaneous connections required varies based on the number and type of POP3 and IMAP4 clients.

Tip   Use the Windows NT Performance Monitor to view current connections.

1. Select the Connections tab.
2. Under Transfer Mode, choose Advanced.
3. Type a number in the appropriate box.

Option	Description
Max no. of Inbound Connections	The maximum number of inbound connections the Internet Mail Service can accept at one time.
Max no. of Outbound Connections	The maximum number of outbound connections the Internet Mail Service can make at one time.
Max no. of Connections to a single host	The maximum number of connections the Internet Mail Service can make to a single host at one time.
Max no. of Messages sent in a connection	The maximum number of messages to be sent during each outbound connection.
Reset default values	Return all options to default settings.

Delivering Messages Using DNS

Use the Connections property page to specify whether all outbound messages will be routed using the routing information in the DNS. This is the default. Domains specified in outbound messages will be looked up in DNS. If the domain is found in DNS, the message will be delivered to the corresponding IP address. If the domain is not found, the message will be returned to the sender with an NDR.

1. Select the Connections tab.
2. Under Message Delivery, select Use domain name service (DNS) to route all outbound messages using DNS queries. This also includes using a Hosts file or Windows Internet Naming System (WINS).
3. Select Dial using if you reach hosts by using a dial-up connection. Choose one of the dial-up connections specified on the Dial-up Connections property page.

For information about specifying message delivery by e-mail domain, see "Delivering Messages by E-mail Domain" later in this chapter. For more information about DNS, see Microsoft Exchange Server Concepts and Planning.

Delivering All Messages to a Single Host

Use the Connections property page to specify that all outbound messages be sent to a single host. If message delivery by e-mail domain is not specified, the message is delivered using the option specified in the Message Delivery section of the Connections property page.

Note   If the domain name of a host is specified, the domain name must be defined in the local Windows NT Server Hosts file or in the DNS. Otherwise, the Internet Mail Service will not start.

1. Select the Connections tab.
2. Select Forward all messages to host, and then type the IP address or host and domain name of the SMTP host. Use the IP address rather than the computer name for the best performance.
This option can be configured to process SMTP mail messages in a round-robin style. For example, you can type a comma-separated list of multiple hosts: host1,host2,host3. The first message will be sent to host1, the second message to host2, the third message to host3, the fourth message to host1, and so on.
3. Select Dial using if you reach the host using a dial-up connection. Choose one of the dial-up connections specified on the Dial-up Connections property page.

For information about specifying message delivery by e-mail domain, see "Delivering Messages by E-mail Domain" later in this chapter.

Delivering Messages by E-mail Domain

Use the Connections property page to define the way messages will be delivered to the destination.

Note   This setting overrides the option you specified under Message Delivery.

1. Select the Connections tab.
2. Under Message Delivery, choose E-Mail Domain.
3. Choose Add.
4. Type the e-mail domain name and specify whether messages will be delivered using DNS or to a specific host.

Option	Description
E-Mail Domain	Type the domain name for which you will specify delivery options. Do not use an ending period after the FQDN.
Use DNS	Select when messages to the specified domain should be delivered using DNS queries.
Forward all messages for this domain to host	Type the host name or IP address of the SMTP host that will process messages for the specified domain. If any host name cannot be resolved, the Internet Mail Service will not start and a Windows NT Event Log message will be generated. This option can be configured to process SMTP mail messages in a round-robin style. For example, you can type a comma-separated list of multiple hosts: host1,host2,host3. The first message will be sent to host1, the second message to host2, the third message to host3, the fourth message to host1, and so on.
Dial using	Select to use a dial-up connection. Choose one of the dial-up connections specified on the Dial-up Connections property page.

For more information about message delivery, see "Delivering Messages Using DNS" and "Delivering All Messages to a Single Host" earlier in this chapter.

Accepting Connections from All Hosts

Use the Connections property page to accept connections from all secure and non-secure hosts. This is enabled by default.

1. Select the Connections tab.
2. Under Accept Connections, select From any host (secure or non-secure).

Accepting Connections from Secure Hosts

Use the Connections property page to accept connections only from hosts using authentication or encryption.

1. Select the Connections tab.
2. Under Accept Connections, select Only from hosts using.
3. Choose Authentication, Encryption, or Auth and Encrypt.

Accepting Connections from Specific Hosts

Use the Connections property page to reject incoming SMTP connections from a single IP address or range of IP addresses. You can specify a range of addresses to reject and make a list of addresses that will be excluded from the restriction. To do this, specify the hosts from which you will accept mail higher in the list than the more general range of hosts from which connections will be rejected.

1. Select the Connections tab.
2. Under Accept Connections, choose Hosts.
3. To add or modify a host, choose Add or Edit.
4. Identify the host by entering the IP address and mask, and then choose an option. Choose OK to return to the Specify Hosts dialog box.

Option	Description
IP Address	Type the IP address of the SMTP hosts that will be accepted or rejected. Use of wildcards is accomplished using the Mask field. If you are specifying only a single IP address to be rejected, you do not need to use the Mask field.
Mask	Type the IP address mask. To control access, the IP address specified is matched against the IP address of the host that is connecting to the Internet Mail Service. The mask specifies which bits are relevant in the match. In Boolean logic, this is equivalent to exclusive-oring the addresses and then anding the result with the mask. If the result is zero, it is a match. For example: IP 192.11.154.0 Mask: 255.255.255.0 Therefore, any IP address in 192.11.154.n would match, where n = 1-254.
Accept connections from this host	Select to allow the specified host to connect to the Internet Mail Service computer.
Only accept from this host if it uses	Select to accept connections from hosts using security. Choose Authentication, Encryption or Auth and Encrypt.
Reject connections from this host	Select to indicate that the specified host is not allowed to connect to the Internet Mail Service computer.
This host is a relay server	Select to override client security requirements in the Connections property page.

1. In the Specify Hosts dialog box, choose an option to identify which clients can submit messages.

Option	Description
Clients can only submit if homed on this server	Select to allow clients to submit messages only if they have a mailbox on this server.
Clients can only submit if authentication account matches submission address	Select to allow clients to submit messages only if their logon account matches the address in the From field of the message.

Setting the Retry Interval

The Internet Mail Service can be set to wait a specified number of hours before retrying a host to which a previous connection attempt has failed. If the Internet Mail Service attempts to deliver a message to an SMTP host for which it has obtained an IP address and does not receive a response from the host, the connector attempts to reconnect after the period of time specified in the Retry interval box.

The first number in the list determines the time the Internet Mail Service will wait between the initial delivery attempt and the first retry. The second number is the amount of time the Internet Mail Service will wait between the first retry and the second retry, and so on. The last specified time interval will be repeated until either the connection is made or the specified time-out value has been reached.

1. Select the Connections tab.
2. Under Connector Message Queues, type the number of hours the Internet Mail Service will attempt subsequent connections.

Option	Description
Retry interval (hrs)	The number of hours to wait before retrying a connection to a host to which delivery has previously been attempted. Values are separated by commas. Periods may be used to indicate partial hours. No spaces are allowed. The default is .25, .5, 1, 4.

For more information about time-out values, see "Specifying Message Time-out Values" later in this chapter.

Specifying Message Time-out Values

Message time-out values can be specified for urgent (high importance), normal, and non-urgent (low importance) messages. If the time-out is reached before the message can be sent, the sender is notified with an NDR, and the message is not sent.

1. Select the Connections tab.
2. Under Service Message Queues, choose Time-outs.
3. Type message time-out values in the appropriate boxes.

Option	Description
Urgent message timeout (hrs)	The maximum amount of time the Internet Mail Service will try to send a message of high importance. The default is 24 hours. The maximum value is 999.
Normal message timeout (hrs)	The maximum amount of time the Internet Mail Service will try to send a message of normal importance. The default is 48 hours. The maximum value is 999.
Non-urgent message timeout (hrs)	The maximum amount of time the Internet Mail Service will try to send a message of low importance. The default is 72 hours. The maximum value is 999.

Controlling Notifications for Queued Mail

1. Select the Connections tab.
2. Under Service Message Queues, choose Time-outs.
3. Select Notify sender for queued mail, and then select the check box for the type of mail for which the sender will be notified.
4. Type the number of hours that will elapse before notification.

Option	Description
Urgent mail every (hrs)	Select to enable notification for messages of high importance. This is the default. Type a value for the number of hours before notification. The default is 4 hours.
Normal mail every (hrs)	Select to enable notification for messages of normal importance. Type a value for the number of hours before notification. When selected, the default is 12 hours.
Non-urgent mail every (hrs)	Select to enable notification for messages of low importance. Type a value for the number of hours before notification. When selected, the default is 24 hours.