Here's the info from MS and a table with which to start. The math is already done!
It was recommended to start with a size of 640M. The lower the number less cache available. You can start higher, but you will have to restart the IS every time you make a change. In my case I saw an improvement at 640M but is was not until I went to 576 that my problem was solved. The higher number you can use to solve the issue, the better.
The number you are going to add/change with ADSI edit is to the right of the = sign. (The corresponding cache size is on the left.)
Modify msExchESEParamCacheSizeMax:
800M msExchESEParamCacheSizeMax=204800
768M msExchESEParamCacheSizeMax=196608
736M msExchESEParamCacheSizeMax=188416
704M msExchESEParamCacheSizeMax=180224
672M msExchESEParamCacheSizeMax=172032
640M msExchESEParamCacheSizeMax=163840
576M msExchESEParamCacheSizeMax=147456
Start ADSI Edit. This tool is included in the Microsoft Windows 2000 Resource Kit
and is also installed with the Windows 2000 support tools. To install the Windows
2000 support tools, run the setup.exe program located in the Support\Tools folder
on the Windows 2000 Server CD-ROM.
On the Action menu, click Connect to.
In the Connection Point section, click Naming Context, and then click Configuration
Container.
In the Computer section, click "Select or type domain or server", and then type
your domain controller.
Click Advanced, click Specify Credentials and then type your user name and
password.
Type "389" (without the quotation marks) in the Port Number box, and then click
LDAP in the Protocol box.
Click OK, and then click OK again. You are then connected to the Configuration
container of your domain controller.
Open the following object:
Services/Microsoft Exchange/<Your organization>/Administrative Groups/<Your
administrative group>/Servers/<Server name>/Information Store
Right-click Information Store, and then click Properties.
On the "Select a property to view" menu, click msExchESEParamCacheSizeMax.
In the "Edit Attribute" box, 163840
Quit ADSI Edit, and then restart the MS Exchange Information Store service.
NOTE: In a multiple domain controller site, this attribute has to replicate to the
Configuration domain controller of the specific Exchange 2000 computer for the
store to register the change.
Good luck,
Let us know how ist works for you.
Dana