When Microsoft released Exchange 2010 they removed support for UDP notificiations and in the process made the Exchange mail server experience less than perfect for the millions of people who still use Outlook 2003. I wrote a blog post about this that has been a real hit, so I can tell people everywhere were desperate for a fix.
Good news, Microsoft will be bring support for UDP back with Exchange 2010 Service Pack 1 Rollup 3!
Full details here: support.microsoft.com/kb/2009942
Thank you Microsoft, about time!