Microsoft KB Archive/248821

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How to Improve IMAP Fetch Response Time with Remote File Server

Article ID: 248821

Article Last Modified on 6/12/2001


  • Microsoft Commercial Internet System 2.0

This article was previously published under Q248821


IMAP service is very slow to fetch a mail message if the mail directory is located on a remote server.


When processing the IMAP fetch command to retrieve a portion of a mail message the IMAP service uses the WinSock TransmitFile API to send the data back to the IMAP client.

The TransmitFile function uses the file system cache to retrieve file data in order to improve performance (for details please refer to the TransmitFile documentation in the Platform SDK).

If the mail store is located on a remote file server, the use of the TransmitFile API can be very inefficient and negatively affect the fetch response time.


The metabase property (MD_IMAP_NO_TRANSMITFILES = 49353 decimal) allows to instruct the IMAP server to switch to another transfer method.

To set this property for a specific IMAP server instance number (in the following sample IMAPSVC/1 is the IMAP server instance), use the following command:

mdutil.exe SET IMAPSVC/1 0 -prop 49353 -utype UT_SERVER -dtype DWORD

You need to stop and restart the IMAP server instance to activate this change.

Keywords: kbprb KB248821