Information coming from the MSExchange team explaining that next RU for Exchange Server 2007 will coincide with Microsoft Security updates day.
This is a heads up that Update Rollup 6 for Exchange Server 2007 SP1 should be out on Tuesday February 10, 2009. As you can see the rollup release date coincides with the day Microsoft issues security patches. No points for guessing that this rollup contains a fix for a security issue. This patch has been assigned a severity rating of critical in Microsoft Security Bulletin Advance Notification for February 2009. As such customers should plan to apply this update rollup to ensure their Exchange Servers are protected.
In addition to the security issues, we have included a change which will allow Internet Explorer 8 to be used for Outlook Web Access 2007. However, this does not include the Outlook Web Access 2007 S/MIME control. We are still working on some changes in the control to make it work better with Internet Explorer 8. Look for an updated version of the S/MIME control in a future rollup.
Read more at source: http://msexchangeteam.com/archive/2009/02/06/450583.aspx