XFOR: Pickup Directory Files Containing Single Period Are Not Padded Correctly (221384)


The information in this article applies to:

  • Microsoft Exchange Server 5.5
  • Microsoft Internet Information Server 4.0
  • Microsoft Commercial Internet System 2.0
This article was previously published under Q221384

SYMPTOMS

When you use Internet Information Service SMTP service to create SMTP mail by copying files to or creating files in the Pickup subdirectory or when you use the Exchange Server Internet Mail Service to create SMTP mail in the Mailroot directory, mail may prematurely end for the recipient.

Each line after the end causes the remote system to interpret the text as a command and generate a "500 Command Unrecognized" error message.

CAUSE

The SMTP service does not explicitly ascertain whether the processed files have a single period on a line by itself in the message contents. Consequently, when a file that contains a single period on a line by itself is copied into the Pickup directory, the period is interpreted as the end of the message, and the message is truncated at the period. Each line after the period causes an error, which produces a "500 Command Unrecognized" error message on the remote system. Unless you run a network trace, the only indication of a problem is that the messages are truncated.

WORKAROUND

When you copy files to the Pickup directory, ensure any single periods are escaped or padded with another period (that is, when you want a period on a line by itself, type two periods).

STATUS

Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article.

MORE INFORMATION

To Reproduce the Problem:
  1. Stop the SMTP service:

    net stop smtpsvc

  2. In Notepad, create the following message and save it in a file called Message.txt in the Pickup directory:
    x-sender: Sender
x-receiver: user1@valid.but.unreachable.host
Subject: Testing.


Testing

.

Testing
<EOF>
  3. Restart the SMTP service.

    net start smtpsvc

    NOTE: The remote user will not see the second "Testing" text.
RFC 821, Section 4.5.2 states: 
4.5.2.  TRANSPARENCY

         Without some provision for data transparency the character
         sequence "<CRLF>.<CRLF>" ends the mail text and cannot be sent
         by the user.  In general, users are not aware of such
         "forbidden" sequences.  To allow all user composed text to be
         transmitted transparently the following procedures are used.

            1. Before sending a line of mail text the sender-SMTP checks
            the first character of the line.  If it is a period, one
            additional period is inserted at the beginning of the line.

            2. When a line of mail text is received by the receiver-SMTP
            it checks the line.  If the line is composed of a single
            period it is the end of mail.  If the first character is a
            period and there are other characters on the line, the first
            character is deleted.
What occurs is that remote systems interpret the "<CRLF>.<CRLF>" sequence as ending the message.

Note that this problem also occurs with the Pickup subdirectory of the Imcdata directory in Exchange Server 5.5.
Modification Type:MinorLast Reviewed:4/28/2005
Keywords:kbbug kbnofix KB221384
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