The "Sender ID Filtering" feature does not work correctly in an Exchange Server 2003 SP2 server

Consider the following scenario. An external server sends e-mail messages to a server that is running Microsoft Exchange Server 2003 Service Pack 2 (SP2). The Exchange Server 2003 SP2 server has the Sender ID Filtering feature enabled. In this scenario, the following symptoms may occur:

• E-mail messages are rejected even though the sending server is included in the Sender Policy Framework (SPF) record.
• E-mail messages are accepted even though the sending server is not included in the SPF record.

This problem occurs because of a problem in the way that the Exchange Sender ID engine applies subnet masks that are defined in the SPF records. The problem may occur if one or more non-class full subnets are defined in the SPF record of the sending domain. The following list contains two examples of non-class full subnets that may be defined in the SPF record of the sending domain:

• v=spf1 ip4:10.0.0.128/25
• v=spf1 ip4:10.0.63.0/18 -all

Note Generally, this problem does not occur when class full subnets are defined in the SPF record of the sending domain. The following list contains two examples of class full subnets:

• 10.0.0.0/16
• 10.0.0.0/24

Hotfix information

A supported hotfix is available from Microsoft. However, this hotfix is intended to correct only the problem that is described in this article. Apply this hotfix only to systems that are experiencing this specific problem. This hotfix might receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next software update that contains this hotfix.

If the hotfix is available for download, there is a "Hotfix download available" section at the top of this Knowledge Base article. If this section does not appear, contact Microsoft Customer Service and Support to obtain the hotfix.

Note If additional issues occur or if any troubleshooting is required, you might have to create a separate service request. The usual support costs will apply to additional support questions and issues that do not qualify for this specific hotfix. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, visit the following Microsoft Web site: Note The "Hotfix download available" form displays the languages for which the hotfix is available. If you do not see your language, it is because a hotfix is not available for that language.

Prerequisites

Because of file dependencies, this software update requires Microsoft Exchange Server 2003 Service Pack 2 (SP2)

Restart requirement

Microsoft Internet Information Services (IIS) and IIS-dependent services are stopped when you install this software update

Hotfix replacement information

This hotfix does not replace any other software updates.

File information

The English version of this hotfix has the file attributes (or later file attributes) that are listed in the following table. The dates and times for these files are listed in Coordinated Universal Time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time item in Control Panel.

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

For more information, click the following article number to view the article in the Microsoft Knowledge Base: For more information, click the following article number to view the article in the Microsoft Knowledge Base: