The "at" sign (@) in an RFC-822 address is sent from Exchange Server 2003 without being converted to another symbol


You can encapsulate an SMTP address in an X.400 address by adding a Request for Comments (RFC) 822 domain-defined attribute (DDA) to the X.400 address. The value of the domain-defined attribute is the SMTP address, as shown in the following example:
c=co; a=admd, p=Org,
In this case, the "at" sign (@) in the RFC-822 address is sent from Microsoft Exchange Server 2003 without being converted to another symbol. However, the "at" sign (@) is invalid in an X.400 address. Therefore, the message is rejected by non-Microsoft Exchange Server message transfer agents (MTAs).

Note In earlier versions of Exchange Server, the invalid "at" sign (@) was converted into a valid character, "a." This behavior prevented problems in communicating with non-Exchange Server MTAs.


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 the problem described in this article. 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.


Because of file dependencies, you must have Exchange Server 2003 SP2 installed on the server to apply this hotfix. For more information, click the following article number to view the article in the Microsoft Knowledge Base:
836993 How to obtain the latest service packs for Exchange Server 2003

Restart requirement

You do not have to restart the computer after you apply this hotfix. However, the Microsoft Exchange MTA Stacks service must be restarted after you apply this hotfix.

Hotfix replacement information

This hotfix does not replace any other hotfixes.

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.
File nameFile versionFile sizeDateTime


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

Article ID: 971337 - Last Review: Sep 9, 2009 - Revision: 1