Slow IMAIL Calls

[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]  

Topic Last Modified: 2006-07-12

The Microsoft® Exchange Server Analyzer Tool examines the Exchange Function Call Log (FCL), the Store.fcl file, for events that exceed a response time of 2.5 seconds for the IMAIL component of the MAPI client.

Exchange FCL IMAIL MAPI component events represent Microsoft Exchange Information Store service (Store.exe) function calls to convert messages to Internet format and from Internet format to MAPI format.

The IMAIL component of Exchange Server is a flexible conversion service that is used by the Microsoft Exchange Information Store service between Internet and MAPI messages. This allows for the interoperability between clients which use RFC-822 or Internet format and clients that use the Exchange Server internal storage format, such as MAPI clients or internal STORE tasks.

Exchange uses the IMAIL mechanism to apply message formats to the content, as defined for Internet domains in Exchange System Manager or as specified by the user per recipient in Microsoft Office Outlook®. If no formatting parameters are passed to IMAIL, IMAIL formats MAPI messages in Summary TNEF (S/TNEF) format for transfer between servers.

If Exchange Server Analyzer finds events in the Store.fcl logging file that reflect a response time for IMAIL component of the MAPI client component function calls from the Microsoft Exchange Information Store service (Store.exe) of more than 2.5 seconds, the Exchange Server Analyzer displays an error.

When cross-component calls from the Microsoft Exchange Information Store service (Store.exe) wait for a response, remote procedure call (RPC) threads can back up behind these requests and lead to Exchange Server performance issues such as delays in server responses to clients.

Slow response times for Exchange Information Store service (Store.exe) function calls to IMAIL can be caused by the following conditions:

  • IMAIL tries to process much data in a message or attachment.

  • Many clients request data conversion.

  • DSAccess requests encounter a slow response.

  • There are bottlenecks on the TEMP and TMP drives.

  • There are ongoing mailbox moves.

  • To resolve this error, take the following steps:

  • Schedule any mailbox moves for off-peak demand intervals.

  • Run the Exchange Server Analyzer for an additional analysis of server issues such as message and attachment size limits. You can download the Exchange Server Analyzer at "Microsoft Exchange Server Best Practices Analyzer Tool v2.7" (

  • Review the articles in the For More Information section of this document.

For more information about Exchange Server Disk Bottleneck issues, see Disk Bottleneck Detected.

For more information about how to size and optimize disks for Exchange Server, see "How to Calculate Your Disk I/O Requirements" and "Best Practices Common to Multiple Architectures" in Optimizing Storage for Exchange Server 2003 (

For more information about best practices for message size limits on Exchange Server, see Maximum outgoing message size has not been set.


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