Setting Connections

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Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1

A connection is initiated whenever a message is sent to or received from a remote server.

Note

Designating the TCP port that the SMTP service uses to receive incoming messages is done when you configure the Simple Mail Transfer Protocol (SMTP) virtual server.

Setting connection limits and imposing connection time-outs can make it more difficult for someone to initiate a malicious attack (such as denial of service) against your virtual server.

Important

You must be a member of the Administrators group on the local computer to perform the following procedure or procedures. As a security best practice, log on to your computer by using an account that is not in the Administrators group, and then use the runas command to run IIS Manager as an administrator. At a command prompt, type runas /User:Administrative_AccountName "mmc systemroot\system32\inetsrv\iis.msc".

Procedures

To configure incoming connections

  1. In IIS Manager, right-click the SMTP virtual server, and then click Properties.

  2. On the General tab, select the Limit number of connections to check box (the default is no limit), and set the following options.

Option Description

Limit number of connections to

When the check box is selected, this option specifies the number of concurrent connections for incoming message delivery. The minimum is 1 connection. When the check box is not selected, no limit is imposed.

Connection time-out (minutes)

Specifies the time allowed before an inactive connection is closed. The default is 10 minutes.

To configure outbound connections

  1. In IIS Manager, right-click the SMTP virtual server, and then click Properties.

  2. Click the Delivery tab, and click Outbound connections.

  3. In the Outbound Connections dialog box, select a check box and set the following options.

Option Description

Limit number of connections to

When the check box is selected, this option specifies the total number of simultaneous outbound connections to all remote domains that can exist at one time. The default is 1,000 connections. The minimum is 1.

This setting can be used to improve system performance in conjunction with the Limit number of messages per connection to check box on the Messages tab.

Time-out (minutes)

Specifies the time allowed before an inactive connection is closed. The default is 10 minutes.

Limit number of connections per domain to

When the check box is selected, this option limits connections to any single remote domain. The default is 100 connections. This number should be less than or equal to the value for the Limit number of connections to option.

TCP port

Designates the TCP port used for outgoing transmissions. The default is port 25. The outgoing port setting can be the same as that for incoming transmissions or it can be different.