An update has been released for Outlook 2007 and can be downloaded and installed manually, but is also being offered via Microsoft Update.
Update KB2768023 for Outlook 2007
This is a non-security update which solves the following issue:
Assume that you connect to some alternative mailboxes, such as auto-mapped mailboxes, modern public folders, and archive mailboxes, on an Outlook 2007 client that is connected to a domain. In this situation, Outlook 2007 only uses the external host name.
If you have Microsoft Update configured to also update other Microsoft applications, then this update will also also be offered via Microsoft Update or has already been updated automatically for you.