By default, additional logging is implemented in
Microsoft Forefront Security for Exchange Server Service Pack 1 (SP1) Update Rollup 3. However, this
new feature may cause queues to form in high mail flow environments in Exchange.
To resolve this issue, install Forefront Security
for Exchange Server with Service Pack 2.
For more information, click the following article number to view the article in the Microsoft Knowledge Base:
Description of Forefront Security for Exchange Server with Service Pack 2
has confirmed that this is a problem in the Microsoft products that are listed
in the "Applies to" section.