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Q153705: XCLN: Messages with Large Attachments Sit in Outbox

Article: Q153705
Product(s): Microsoft Exchange
Version(s): WINDOWS:4.0,5.0
Operating System(s): 
Keyword(s): kbusage
Last Modified: 02-APR-1999

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The information in this article applies to:

- Microsoft Exchange Windows 3.x client, versions 4.0, 5.0 
- Microsoft Exchange Windows 95/98 client, versions 4.0, 5.0 
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SUMMARY
=======

If Microsoft Exchange is installed in a Token Ring environment and Microsoft
Exchange Windows 3.x clients are configured so that the connection to the
Microsoft Exchange Server is made via IPX/SPX, the clients might be unable to
send messages with attachments larger than approximately 10K. The messages will
sit in your Outbox and will never be sent to the Microsoft Exchange Server. At
this point, any subsequent messages will also fail to leave the Outbox.

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

This behavior can occur as a result of mismatched network packet frame sizes
between the Microsoft Exchange client workstation and the Microsoft Exchange
Server.


Token-Ring adapters can have network packet frame sizes of more than 16K as
opposed to Ethernet, which generally uses 1500 byte frames. Usually the software
drivers for Token-Ring cards use a frame size of approximately 4K, but different
manufacturers may use different values. In a NetWare environment, if the frame
sizes on the computer that is running the Microsoft Exchange Client and the
computer running Microsoft Exchange Server do not match, the client will report
network errors when sending large e-mail messages or when moving or copying
items from the user's Inbox to a public folder. The error text notes the
operation that failed and attributes it to "network problems." For example, if
the operation being attempted was copying a message from the Inbox to a public
folder, the error text would be "An item could not be copied. Network problems
are preventing a connection to the Microsoft Exchange Server computer."

To solve this problem, adjust the frame sizes on the server and client to match.
When the client Token-Ring driver loads, take note of the maximum packet size
that it reports. You will need to set the server's maximum packet size to match
this value. For the Token.com driver that ships with NetWare 3.12 and 4.x, the
default size that it will report is 4210.

To change the maximum packet size on the server, start the Network application in
Control Panel, highlight the Token-Ring adapter card entry, click the configure
button, and then change the setting and save it. If you are using the Windows NT
driver for IBM Token- Ring, use the registry to configure the Maximum Packet
Size. This is a DWORD registry entry with a path of
KEY_LOCAL_MACHINE\System\CurrentControlSet\Services\IBMTokx\Parameters (where x
is the optional adapter number) and the parameter is MaximumPacketSize. Use the
decimal value from the client's driver specification. Restart the server for the
new setting to take effect.

For more information on configuring other Token Ring adapters, refer to the
manufacturer documentation included with the adapter.

For Windows 95 Clients, to force even length Packets, go to Start, Settings,
Control Panels, Network, highlight the "IPX/SPX" transport, click properties,
click on the Advanced tab, and set "Force Even Length Packets" value to "yes".

Additional query words:

======================================================================
Keywords          : kbusage 
Technology        : kbExchangeSearch kbExchange500 kbExchange400 kbExchangeClientSearch kbZNotKeyword kbZNotKeyword2 kbZNotKeyword3 kbExchange400Win95 kbExchange500Win95
Version           : WINDOWS:4.0,5.0
Issue type        : kbprb

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