The mailing lists are having problems as the server they use is not working correctly. The team in the UK is aware of the issue and is actively working on a solution.
April 22: The servers are now up and working properly (details in my comment below).
I often receive email from people asking questions that typically end up being sent to xen-users for a quick response. I wanted to remind people that we have a great search utility at http://xen.markmail.org that will search every xen mailing list email sent since the mailing lists were started. Their are currently 117,600 messages in the tool for searching and the user interface is very impressive. If you haven’t tried this tool, be sure to check it out.