SMTP: Attachments Seem Corrupted or Garbled

 Last reviewed: October 20, 1997
Article ID: Q118487
2.10 3.00 MS-DOS

The information in this article applies to:

  • Microsoft Mail Gateway to SMTP, versions 2.1 and 3.0

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.

Additional reference words: 3.00 hex garbled corrupted
KBCategory: kbusage
KBSubCategory: MailGWSMTP

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Last reviewed: October 20, 1997
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