Thanks for the feedback Charlie,
my objective is to see wether it can be done with SME Server specifically. Wether it is within a hosted environment or upgrading a stock CentOS install (Xen based or not). If it can be done based on a hosted server, it should be easy with a big 'in house' server.
Basically the question is: can a default CentOS install be 'upgraded' to a full blown SME Server?
Thanks,
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