SMTP: Attachments Seem Corrupted or Garbled (118487)


The information in this article applies to:

  • Microsoft Mail Gateway to SMTP 2.1
  • Microsoft Mail Gateway to SMTP 3.0
This article was previously published under Q118487

SYMPTOMS

Attachments of mail messages from the Microsoft Mail Gateway to SMTP may appear as in the body of messages and seem corrupted. They may also seem corrupted if you try to open them with their programs.

CAUSE

Attachments are coming in encoded in a format not supported by the SMTP Gateway.

The SMTP Gateway supports the TEXT and UUENCODE formats of experimental protocol RFC 1154 ONLY. The uuencode used is Sun's uuencode 5.

The SMTP Gateway does not support:

  • uuencoded files sent using the hex format instead of uuencode
  • AppleSingle file format
  • AppleDouble file format

RESOLUTION

Check with the message sender to ensure that attachments are uuencoded in accordance to RFC 1154 section 4.7 and the uuencode format, or that text attachments use the TEXT format.

If the sender is on a Macintosh, ensure that the gateway to SMTP uuencodes the attachment and either uses MacBinaryII or strips off the resource fork of the file before sending it out.

You can verify what encoding type is being received by looking at the header lines of the incoming message in the log file (m:\log\smtpgate.log). The encoding line will display the line count and format of all attachments.

An example of encoding that the SMTP gateway can understand is below:

Header: Encoding: 2 TEXT, 1596 UUENCODE

An example of encoding types the SMTP gateway does not understand is:

Header: Encoding: 2 TEXT, 391 HEX

NOTE: The CC:Mail SMTP Gateway is configured by default to encode outgoing SMTP attachments in uuencode format. Turning on the uuencode option with the CC:Mail gateway turns on encoding using the hex format. Using the option to uuencode the complete message encodes the body as well as the attachment portion, rendering the message unreadable by MS Mail users, and (probably) by users with accounts on the SMTP host.

MORE INFORMATION

Here are the definitions of text, hex, and uuencode formats from the experimental protocol RFC 1154 specification:

4.1. Text

This indicates that the message is in no particular encoded format, but is to be presented to the user as is.

The full range of the ASCII character set is used. The message is expected to consist of lines of reasonable length (less than 1000 characters).

On some transport services, only the 7-bit subset of ASCII can be used. Where full 8-bit transparency is available, the text is assumed to be ISO 8859-1 [3] (ASCII-8).

4.3. Hex

The encoding indicates that the body part contains binary data, encoded as 2 hexadecimal digits per byte, highest significant nibble first.

Lines consist of an even number of hexadecimal digits. Blank lines are not permitted. The decode process must accept lines with between 2 and 1000 characters, inclusive.

4.7. uuencode

The uuencode keyword specifies a section consisting of the output of the uuencode program supplied as part of UUCP.

Modification Type:MajorLast Reviewed:10/2/2003
Keywords:KB118487
©2003 Microsoft Corporation. All rights reserved.