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Enable Fast Message Retrieval for IMAP4

[This topic is intended to address a specific issue called out by the Exchange Server Analyzer Tool. You should apply it only to systems that have had the Exchange Server Analyzer Tool run against them and are experiencing that specific issue. The Exchange Server Analyzer Tool, available as a free download, remotely collects configuration data from each server in the topology and automatically analyzes the data. The resulting report details important configuration issues, potential problems, and nondefault product settings. By following these recommendations, you can achieve better performance, scalability, reliability, and uptime. For more information about the tool or to download the latest versions, see "Microsoft Exchange Analyzers" at http://go.microsoft.com/fwlink/?linkid=34707.]  

Topic Last Modified: 2008-01-18

The Microsoft Exchange Server Analyzer Tool queries the Active Directory directory service to determine the value of the serialNumber attribute for all objects with an object class of msExchExchangeServer. If the string value includes Version 5.5, the computer is running Microsoft Exchange Server version 5.5. If the string value includes Version 6.0, the computer is running Exchange 2000 Server. If the string value includes Version 6.5, the computer is running Exchange Server 2003. If the string value includes Version 8.0, the computer is running Exchange Server 2007.

The Exchange Server Analyzer also queries the Active Directory directory service to determine the value for the serverRole attribute of the Exchange server object. A value of 1 for the serverRole attribute indicates that the Exchange server has been configured as a front-end server. A value of 0 indicates that the Exchange server is not configured as a front-end server.

The Exchange Analyzer then queries the Win32_Service Microsoft Windows Management Instrumentation (WMI) class to determine the value of the Started key for the IMAPv4 service (IMAP4Svc). A value of False indicates that the IMAPv4 service is not running on this Exchange server. A value of True indicates that the IMAPv4 service is running.

The Exchange Analyzer then reads the data found in the LM/Imap4Svc/<IMAP4INSTANCE>/1016/ServerState property to determine the state of the IMAPv4 virtual server instance running on the Exchange Server. The state codes, and the corresponding states, are as follows:

 

State Code State

1

Starting

2

Started

3

Stopping

4

Stopped

5

Pausing

6

Paused

7

Continuing

Finally, the Exchange Analyzer reads the data found in the LM/Imap4Svc/<IMAP4INSTANCE>/49853/ImapEnableFastMsgRetrieval property in the Internet Information Services (IIS) metabase to determine whether the Internet Message Access Protocol version 4 rev 1 (IMAP4) Fast Message Retrieval is enabled on the Exchange Server.

If the Exchange Analyzer determines that all the following conditions are true, the Exchange Analyzer displays a warning.

  • The computer is running Exchange Server 2003.

  • The computer is not configured as an Exchange Server 2003 front-end server.

  • The IMAPv4 service and virtual server are running.

  • IMAP4 Fast Message Retrieval is not enabled on the Exchange Server.

This warning indicates that the Exchange Server 2003 back-end server may be experiencing a decreased level of performance that could be remedied by enabling IMAP4 Fast Message Retrieval.

Internet messaging client computers that access Exchange Server by using IMAP4 use the streaming store (.stm file) for reading and writing mailbox data that is stored as MIME content. If you use the Move Mailbox functionality in Exchange System Manager or Active Directory Users and Computers to move a mailbox that is accessed by an IMAP4 client, the data in the moved mailbox is promoted into the Extensible Storage Engine store (.edb file), and the content is converted from MIME content to MAPI content.

When the IMAP4 client logs on, exact message sizes are calculated, and MAPI-to-MIME conversion of the mailbox data occurs in memory and on the disk of the server. The conversion on disk occurs in the Microsoft Windows TMP folder, which is usually not on a disk that has many spindles. The disk cannot handle the large number of I/O requests caused by a conversion of so many messages. Therefore, a user may experience long delays (up to several minutes) when the user does something as simple as switching between messages on the client. This behavior occurs because the disk that the TMP folder is located on cannot keep up with all the disk activity that Exchange generates to convert messages.

In extreme cases, very large temporary files may be created on the Exchange server when this behavior occurs. In some cases, without correct planning or available server resources, the conversion from MIME to MAPI may also cause system latencies. This may cause IMAP4 clients to experience long delays during logon because of the requirement for exact message size calculation. You can improve performance by enabling fast message retrieval for IMAP4 clients.

To Enable Fast Message Retrieval for an IMAP4 Virtual Server
  1. Follow the guidance in the core Exchange Server 2003 documentation, "How to Enable Fast Message Retrieval for an IMAP4 Virtual Server" (http://go.microsoft.com/fwlink/?LinkId=108282).

For more information about performance issues with IMAP4 clients, see Microsoft Knowledge Base article 329067, "Information about performance issues that occur when you use POP3, IMAP, or WebDAV clients, such as Entourage, after you move mailboxes in Exchange Server 2003 or in Exchange 2000 Server" (http://go.microsoft.com/fwlink/?linkid=3052&kbid=329067).

 
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