XCON: Leading Space in Distribution List Name Is Causing Non-Delivery Report

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This article was previously published under Q279209

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SYMPTOMS

Mail users may see non-delivery reports (NDRs) if the name of a distribution list (DL) that they are a member of begins with a space.

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When the directory is searched, to expand the DL membership, an LDAP query is constructed. Spaces and other special characters must be escaped following specific guidelines in Requests for Comments (RFC).

In distinguished names, spaces are escaped with a backslash (\) in accordance with RFC 1779. However, the distinguished name escaping in RFC 1779 does not apply to other attributes, including CN. Because Exchange 2000 reads the members in the RFC 1779 distinguished name format, but issue searches based on CN, Exchange 2000 has special code that unescapes characters that are escaped in the RFC 1779 format.

Searches may not work because LDAP is not expecting the space to be escaped. You can quickly verify this using Ldp.exe. If the name of the DL is " MyDL," the search (CN=\ MyDL) does not find the object, but the search for (CN=MyDL) does.

Now, even with CN attributes, there are several characters Exchange 2000 escapes in the RFC 2254 format. These characters are the parentheses (()) and asterisk (*). The RFC 2254 escaping mechanism looks like \XY, where XY are the hexadecimal digits that correspond to the ASCII character code:

           Character       ASCII value
           ---------------------------
           *               0x2A
           (               0x28
           )               0x29
           \               0x5C
           NUL             0x00
           space           0x20

The character must be encoded as the backslash (\) character (ASCII 0x5C) followed by the two hexadecimal digits that represent the ASCII value of the encoded character. The case of the two hexadecimal digits is not significant. Therefore, if you construct the LDAP query for your DL named " MyDL," following these guidelines, it looks like "CN=\20MyDL," which resolves correctly.

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RESOLUTION

To resolve this problem, obtain the latest service pack for Microsoft Exchange 2000 Server. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

301378 (http://support.microsoft.com/kb/301378/EN-US/ ) XGEN: How to Obtain the Latest Exchange 2000 Server Service Pack

The English version of this fix should have the following file attributes or later:

Component: Transport Core

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File name	Version
Phatq.dll	6.0.25.4418

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STATUS

Microsoft has confirmed that this is a problem in Microsoft Exchange 2000 Server. This problem was first corrected in Microsoft Exchange 2000 Server Service Pack 1.

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