Don't know about one-to-one emails, but comments in forums have certainly been found to be libellous and damages awarded in the UK. It certainly isn't necessary to live in the same town as your libeller to sue 'em, nor is freedom of speech unlimited even in the US. As far as I am aware the educational version of Photoshop can be used for work, and upgraded as a standard version, though I'm not at all clear why you raise that (or the tax issue for that matter).