Microsoft KB Archive/221384

= XFOR: Pickup Directory Files Containing Single Period Are Not Padded Correctly =

Article ID: 221384

Article Last Modified on 10/28/2006

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APPLIES TO


 * Microsoft Exchange Server 5.5 Standard Edition
 * Microsoft Internet Information Server 4.0
 * Microsoft Commercial Internet System 2.0

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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:  Stop the SMTP service:

net stop smtpsvc

  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   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: <pre class="fixed_text">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.

Keywords: kbbug kbnofix KB221384

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