XCON: External Domain Name System Resolver Does Not Handle CNAME Records That Point to Other CNAME Records (332189)


The information in this article applies to:

  • Microsoft Exchange 2000 Server
This article was previously published under Q332189

SYMPTOMS

Microsoft Exchange 2000 Server cannot send messages to remote domains that have a mail exchanger (MX) record that is a pointer to an alias (CNAME) record that is in turn a pointer to another CNAME record instead of being a pointer to an address (A) record.

RFC 2821 (section 3.6) states that domain names must be resolvable to MX records and A records from the domain part of a message. RFC 2821 also permits CNAME records that have targets that can be resolved in turn to MX records or A records.

Not all domains on the Internet comply with the practice that the CNAME record must point to an MX record or to an A record, and these domains may have CNAME records that point to another CNAME record. The design of Exchange 2000 did not account for this possibility.

RESOLUTION

A supported hotfix is now available from Microsoft, but it is only intended to correct the problem that is described in this article. Only apply it to systems that are experiencing this specific problem. This hotfix may receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next Exchange 2000 service pack that contains this hotfix.

To resolve this problem immediately, contact Microsoft Product Support Services to obtain the hotfix. For a complete list of Microsoft Product Support Services telephone numbers and information about support costs, visit the following Microsoft Web site:

http://support.microsoft.com/contactus/?ws=support

Note In special cases, charges that are ordinarily incurred for support calls may be canceled if a Microsoft Support Professional determines that a specific update will resolve your problem. The usual support costs will apply to additional support questions and issues that do not qualify for the specific update in question.
Component: Router

The English version of this hotfix has the file attributes (or later) 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 tool in Control Panel. 
   Date         Time     Version        Size        File name
   ------------------------------------------------------------
   06-Nov-2002  18:40      6.0.6360.0    524,288   Reapi.dll
   06-Nov-2002  18:46      6.0.6360.0    311,296   Resvc.dll
Note Because of file dependencies, this update requires Exchange 2000 Service Pack 3 (SP3). For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

301378 How to Obtain the Latest Exchange 2000 Server Service Pack

STATUS

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section of this article.
Modification Type:MinorLast Reviewed:10/10/2005
Keywords:kbHotfixServer kbQFE kbbug kbExchange2000preSP4fix kbfix kbQFE KB332189 kbAudITPRO
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