Check this out, Sembee just posted an awesome blog
Source: http://www.sembee.co.uk/archive/2008/05/12/77.aspx
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A new tool from the Microsoft Exchange team, currently in prototype/development may well be something to help you. https://www.testexchangeconnectivity.com/ can currently test Autodiscover, Outlook Anywhere (which should work for Exchange 2003 and Exchange 2007), ActiveSync and inbound SMTP.
flaphead.com 