XFOR: 5.0 Mapi Causes IMS to be 10% Slower

The Internet Mail Service (IMS) is 10 percent slower across the board using the Mapi32.dll in comparison with the Microsoft Exchange Server 4.0 Mapi32.dll.

The problem is due to the changes made to MAPI and EMSMDB to handle access from multiple security contexts.

Microsoft has confirmed this to be a problem in Microsoft Exchange Server version 5.0. This problem was corrected in the latest Microsoft Exchange Server 5.0 U.S. Service Pack. For information on obtaining the service pack, query on the following word in the Microsoft Knowledge Base (without the spaces):

The net result of the change planned for Microsoft Exchange Server 5.0 Service Pack 1 is a 78 percent increase in throughput in the IMS over 5.0 (and a 40 percent improvement over 4.0). There will probably be similar improvements in any single-security context application (for example, Microsoft Exchange Client, Outlook, and so on.)

To test the change, run the IMS (or any single-security context MAPI application) and observe that performance is better.