In a blog post on Windows Live Wire, Microsoft has announced that it will discontinue the DAV protocol for accessing Hotmail on September 1, 2009.  DAV (or WebDAV) is an older protocol, not suited to large inboxes, and with free POP3 access for all Hotmail accounts now available, the DAV protocol is no longer needed.

If you are still using DAV to access your email, for example from Outlook (not the Outlook Connector), or from Outlook Express or Apple’s Entourage, you’'ll need to make some changes before September.  From the blog post:

• If you use Microsoft Office Outlook to view Hotmail, download Office Outlook Connector (it’s free) to continue accessing your Hotmail within Outlook 2003 or 2007. If you’re using Outlook 2002, you’ll need to change the settings in your Outlook program. Learn more about this from the Windows Live Solution Center article on Hotmail and Outlook.
• If you use Outlook Express to view Hotmail, you can download Windows Live Mail (recommended) for free, or change your settings in Outlook Express to continue accessing your Hotmail there. Learn more about this from the Windows Live Solution Center article on Hotmail and Outlook Express.
• If you use Entourage to view Hotmail, you’ll need to change the settings in Entourage to continue receiving Hotmail messages there. Learn more about this from the Windows Live Solution Center article on Hotmail and Entourage.