I hope you saw how easy it is to get up and running with web services using
XML-RPC. For most cases XML-RPC is more than enough. It has its disadvantages,
in particular in terms of security. But, in most cases this is not a bit issue
(remember that all your email is still transferred unencrypted, i.e. basically
anyone interested enough could read it). All in all I think XML-RPC is fun.