Topic Last Modified: 2005-11-18

The Microsoft® Exchange Server Analyzer Tool queries the Win32_Directory Microsoft Windows® Management Instrumentation (WMI) class to determine the value of the Compressed key for the Simple Mail Transfer Protocol (SMTP) PickUp folder. If the Exchange Server Analyzer finds the value for Compressed set to True, a warning is displayed.

When messages arrive at the Exchange computer through the SMTP service, the data is written to the hard disk as an .eml file. By default, these files are stored in the <drive>:\Program Files\Exchsrvr\Mailroot folder on the same partition that Exchange is installed on. If the folder where the SMTP PickUp data is stored has file compression turned on, Exchange performance may be severely degraded. Therefore, compression for the folder where the SMTP PickUp data is stored is not supported.

If you receive this warning, you must turn off compression on the folder where the SMTP PickUp data is stored, or you must move the SMTP PickUp data to a folder that is not compressed.

Microsoft does not support the storage of Exchange data files on a compressed volume. When you store your Exchange data files on a compressed volume, the additional overhead significantly affects Exchange performance. The Exchange data files include all the following files:

To turn off file compression on a given folder

  1. Right-click the folder where you want to turn off file compression, and then click Properties.

  2. On the General tab, click Advanced.

  3. In the Advanced Attributes dialog box, clear the Compress contents to save disk space check box, and then click OK.

For more information about moving the PickUp folder, see the Microsoft Knowledge Base article, "How to change the Exchange 2003 SMTP Mailroot folder location" (