XFOR: Inbound Mail Failures on BinHex 4.0 Attachments

- Microsoft Exchange Server, version 4.0

SYMPTOMS

The Microsoft Exchange Internet Mail Connector (IMC) administrator may receive inbound mail failures when trying to process BinHex 4.0 attachments from a Novell Groupwise 4.1 SMTP mailer. The inbound message will be placed in a file called Message.txt and attached to the Inbound Mail Failure notification.

CAUSE

The problem is that the Novell Groupwise 4.1 BinHex 4.0 encoder uses run length encoding when it encounters two characters in a row that are the same. The IMC fails the content conversion because it checks the length character to make sure it is 3 or greater, which is the only time it is efficient to use run length encoding. If the IMC finds a 1 or 2, it considers the message content invalid and content conversion fails.

MORE INFORMATION

The BinHex 4.0 compression will find and compress repeating characters, or a "run" of the same characters. The specification requires three characters to describe the run length encoding. The first character is the repeating character, followed by a "90" to indicate compression, then a character is dictating the number of times the first character is repeated. For example, the left-hand side below would be compressed into what is displayed to the right of the arrow:

   11 22 22 22 22 22 22 33   ->   11 22 90 06 33

STATUS

Microsoft has confirmed this to be a problem in Microsoft Exchange Server version 4.0. This problem was corrected in the latest Microsoft Exchange 4.0 U.S. Service Pack. For information on obtaining the service pack, query on the following word in the Microsoft Knowledge Base (without the spaces):