Update 7/14/11: When contacting Microsoft Customer Support to obtain the Interim Update, you can reference KB 2581545 (please note that the article will be available at a later date on support.micr...
Updated Jul 01, 2019
Version 2.0
Blog Post
@All - Thanks for your patience, and I apologize for your inability to obtain the Interim Update. When you call into support you can reference KB 2581545. Please note that this KB article has not been published, so it will not resolve on support.microsoft.com (it's forthcoming). When you receive this IU, you must install it on all CAS and Mailbox servers that have SP1 RU4 installed.
@Vojin - You can uninstall the IU, by going into the Control Panel, selecting "Uninstall a Program" and clicking "View Installed Updates".
@Gulab and Brian - You can either uninstall SP1 RU4 which will revert your Exchange server back to the previously installed rollup/SP version, or you can obtain the IU from support and stay on SP1 RU4.
Ross