When an IMAP4 client sends a FETCH (bodystructure) request to a server that is running the Exchange Server 2007 IMAP4 service, a corrupted response is sent as a reply

When an Internet Message Access Protocol version 4 (IMAP4) client sends a FETCH (bodystructure) request for a specific message to a server that is running Microsoft Exchange Server 2007, the Exchange 2007 server returns an incorrect response that the IMAP4 client interprets as a corrupted message.

This issue occurs when the Exchange 2007 server responds to a FETCH (bodystructure) request. The response message does not contain a Content-Transfer-Encoding field in the MIME header of each body part of the message. When this field is missing, the Exchange 2007 server sets the body-fld-enc parameter of the Content-Transfer-Encoding field to the NIL value. However, according to RFC 3501, this parameter should be set to 7BIT value. According to RFC 3501, the body-fld-enc parameter may only contain the following string values

• 7BIT
• 8BIT
• BINARY
• BASE64
• QUOTED-PRINTABLE

If the body-fld-enc parameter contains the NIL value, some IMAP4 clients might exhibit unexpected behavior when they receive such a response from the Exchange 2007 server.

For more information about the Content-Transfer-Encoding field and the body-fld-enc parameter, visit the Internet Engineering Task Force (IETF) to review the following RFCs:

• RFC 3501:
  http://www.ietf.org/rfc/rfc3501.txt
• RFC 2045:
  http://www.ietf.org/rfc/rfc2045.txt

To resolve this issue, download and install Update Rollup 2 for Exchange Server 2007 Service Pack 2.

Prerequisites

The following list contains prerequisites for the update rollup:

• You must have Microsoft Exchange Server 2007 Service Pack 2 installed to install this update rollup. For more information about how to obtain the latest Exchange Server 2007 service pack, click the following article number to view the article in the Microsoft Knowledge Base:
  937052 How to obtain the latest service pack or update rollup for Exchange 2007

For more information about Update Rollup 2, click the following article number to view the article in the Microsoft Knowledge Base: