Error message when you try to move an e-mail message that includes a large attachment from a .pst store to an IMAP4 folder in Outlook: "Can't move the item. This server responded that this message is too big"

Consider the following scenario. On a client computer in a Microsoft Exchange 2000 Server organization, you configure Microsoft Outlook to include two e-mail accounts. You configure one of the e-mail accounts to deliver mail to a personal folder (.pst) file, and you configure the other e-mail account to connect to an IMAP4 server.

In this scenario, you try to move a message in Outlook that includes a large attachment from a folder in the .pst store to an IMAP4 folder. When you try to do this, you receive an error message that resembles the following error message:Note An event that corresponds to this error message may not be logged in the event log.

This issue occurs because the IMAP service is not configured to accept messages that include large attachments.

To resolve this issue, you must enable the IMAP4 service to accept larger attachments. Additionally, you must increase the connection time-out interval.

To receive event log information about the error, enable diagnostics logging on the IMAP service.

How to enable the IMAP4 service to accept larger attachments

To enable the IMAP4 service to accept larger attachments, configure the AppendSizeLimit registry entry on the server that is running Exchange Server. To do this, follow these steps.

Warning Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by using another method. These problems might require that you reinstall the operating system. Microsoft cannot guarantee that these problems can be solved. Modify the registry at your own risk.

1. On the Exchange Server server, start Registry Editor.
2. Locate and then click the following registry subkey:
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\IMAP4SVC\Parameters
3. Create the following registry entry under this subkey:
   Name: AppendSizeLimit
   Value type: DWORD
   Value data: The size of the attachment for which you want to allow, in kilobytes. For example, type a value of 15360 to allow for an attachment size of up to 15 MB.
4. Exit Registry Editor.

How to increase the connection time-out interval

To do this, follow these steps:

1. Start Exchange System Manager.
2. Expand Administrative Groups, and then expand the administrative group that you want. For example, expand First Administrative Group.
3. Expand Servers, expand the name of the server that you want, and then expand Protocols.
4. Expand IMAP4, right-click the IMAP4 virtual server that you want, and then click Properties.
5. On the General tab, enter the value that you want in the Connections time-out (minutes) box.
6. Exit Exchange System Manager.

How to enable diagnostics logging

To receive event log information about this issue, you must enable diagnostics logging on the IMAP4 service. To do this, follow these steps:

1. Start Exchange System Manager.
2. Expand Administrative Groups, and then expand the group that you want. For example, expand First Administrative Group.
3. Expand Servers, right-click the name of the server that you want, and then click Properties.
4. Click the Diagnostics Logging tab, and then click IMAP4Svc in the Services box.
5. In the Categories box, click Client Action, click Minimum under Logging Level, and then click OK.
6. Exit Exchange System Manager.

After you enable diagnostics logging, an event that resembles the following event is logged in the Application log when you try to move a large attachment to an IMAP4 folder:

Event ID: 2001
Event Type: Error
Event Source: IMAP4SVC
Event Category: Client Action
Date: Date
Time: Time
User: N/A
Computer: Server_Name
Description: Client "User_Name@Domain.com" requested to append a message which size (29553997 bytes) exceeds the server's configured limit (20971520 bytes). This limit can be increased by creating a DWORD value "AppendSizeLimit" under the "HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\IMAP4SVC\Parameters" key in the registry and setting its value to the desired maximum message size in kilobytes.
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For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.
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