XFOR: Quoted-Printable Encoded Messages Stay in IMC

ID: Q146993

The information in this article applies to:

Microsoft Exchange Server, version 4.0

SYMPTOMS

The Microsoft Exchange Server version 4.0 Internet Mail Connector (IMC) may have problems sending outbound messages that are encoded quoted-printable. In addition, the IMC's performance will gradually degrade until it is no longer capable of delivering additional messages past the message stuck in the queue.

CAUSE

Messages sent with an attachment that have a Content-Transfer-Encoding type of quoted-printable get stuck in the outgoing IMC queue indefinitely and eventually cause the IMC to hang. In order for a message to have a content encoding type of quoted-printable, a message must be sent with an attachment that contains the proper ratio of ASCII to extended ASCII characters.

The problem occurs because IMAIL is not appending the appropriate "carriage return line feed" (CR LF) at the end of the message. The IMC appends the "dot carriage return line feed" (. CR LF) but since this isn't an appropriate end of message character string, the host keeps waiting for more data which never arrives.

All SMTP messages should always end in CRLF.CRLF. The hex representation for this ending sequence is:


   0D 0A 2E 0D 0A

Archived IMC messages can be analyzed using a hex editor tool such as List. The hex dump below is the end of an actual message that was stuck in an IMC's outgoing queue:


   00000110 3E 33 3E 3E 59 3E 4E 3E 34 2F 39 37 3E 3E 3E 3E
   00000120 33 3E 0D 0A 3D 31 41 2E 0D 0A

Note that the last 5 bytes of the example message above were:


   31 41 2E 0D 0A

The first two bytes were actual message data. The last three bytes were appended to the message by the IMC as part of the ending sequence. However, the first two bytes (CRLF or 0D 0A in hex) were not appended to the end of the message by IMAIL. Thus, the ending sequence was invalid and the host didn't know that the IMC was finished sending data.

STATUS

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

S E R V P A C K

Additional query words:

Keywords : kbbug4.00
Version : winnt:4.0
Platform : winnt
Issue type : kbbug