DOCUMENT:Q193035  30-APR-1999  [exchange]
TITLE   :XFOR: Ability to Restrict Size of Headers Contained in Message
PRODUCT :Microsoft Exchange
PROD/VER:WinNT:5.5
OPER/SYS:
KEYWORDS:exc55sp2fix

======================================================================
-------------------------------------------------------------------------------
The information in this article applies to:

 - Microsoft Exchange Server, version 5.5 
-------------------------------------------------------------------------------


IMPORTANT: This article contains information about editing the registry.
Before you edit the registry, make sure you understand how to restore it
if a problem occurs. For information about how to do this, view the
"Restoring the Registry" Help topic in Regedit.exe or the "Restoring a
Registry Key" Help topic in Regedt32.exe.

SYMPTOMS
========

Messages sent from a Microsoft Exchange Server computer (originating from an
Exchange client or through an external gateway) with a large number of
recipients may prevent the Microsoft Mail for PC Networks client from
downloading new messages. This problem occurs if the messages are directed to
one or more recipients on a Microsoft Mail for PC Networks postoffice.

CAUSE
=====

The Microsoft Mail for PC Networks client has a limitation in the size of header
that can exist within a message. If a header is larger than 32 KB (or 64 KB with
a later fix), the above symptoms will occur. More information about this
limitation can be found in the following Knowledge Base article:

   Q147040 PC Win: Large Recipient List Stops Download of New Mail

RESOLUTION
==========

To resolve this problem, obtain the latest service pack for Exchange Server
version 5.5. For more information, please see the following article in the
Microsoft Knowledge Base:

   Q191014 XGEN: How to Obtain the Latest Exchange Server 5.5 Service Pack


The English version of this fix should have the following file attributes or
later:

   Component: Microsoft Mail Connector Interchange

   File Name   Version
   ----------------------
   Mt.exe      5.5.2365.0
   Mtmsg.dll   5.5.2365.0

STATUS
======

Microsoft has confirmed this to be a problem in Microsoft Exchange Server
version 5.5. This problem was first corrected in Exchange Server 5.5 Service
Pack 2.


MORE INFORMATION
================

To work around this limitation, obtain the latest release of the Microsoft Mail
Connector Interchange software as indicated above. There is a new registry key
called "Message Header Size Limit".

WARNING: Using Registry Editor incorrectly can cause serious problems that may
require you to reinstall your operating system. Microsoft cannot guarantee that
problems resulting from the incorrect use of Registry Editor can be solved. Use
Registry Editor at your own risk.

For information about how to edit the registry, view the "Changing Keys And
Values" Help topic in Registry Editor (Regedit.exe) or the "Add and Delete
Information in the Registry" and "Edit Registry Data" Help topics in
Regedt32.exe. Note that you should back up the registry before you edit it. If
you are running Windows NT, you should also update your Emergency Repair Disk
(ERD).

1. Log on to the Microsoft Exchange Server computer where the Microsoft Mail
   Connector is installed.

2. Start Registry Editor (Regedt32.exe) and go to the following key:

   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeMSMI
   \Parameters

3. On the Edit menu, click Add Value.

4. Enter the following:

   Value Name: Message Header Size Limit
   Data Type:  REG_DWORD
   Value:      <see below>

5. Click OK and quit Registry Editor.

If this registry value is present and set to a positive number, that is the size
limit in bytes of the header portion of the MAI file for all outgoing messages
from the Microsoft Mail Connector (MSMI). Incoming messages are not affected by
this setting. If this registry value is not present or the size limit is set to
0, the MSMI will work as before, that is, no size limits will be imposed.

If this registry value is being used, then a message with a header size that is
larger than the header size limit will be returned to the sender. An error
message is logged in the event log with event ID 2604. This event message gives
the address of the sender and the MsgID of the returned message.

Additional query words: msmi header msmail ndr
======================================================================
Keywords          : exc55sp2fix 
Technology        : kbExchangeSearch kbExchange550 kbZNotKeyword2
Version           : WinNT:5.5
Issue type        : kbbug
Solution Type     : kbfix

=============================================================================

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS
PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND.  MICROSOFT DISCLAIMS
ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES
OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.  IN NO
EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR
ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL,
CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF
MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE
POSSIBILITY OF SUCH DAMAGES.  SOME STATES DO NOT ALLOW THE EXCLUSION
OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES
SO THE FOREGOING LIMITATION MAY NOT APPLY.

Copyright Microsoft Corporation 1999.