(2-part post):
You're starting to receive 'dodgy' emails for one of two reasons. Either a spammer has picked up your email address from somewhere on the web (perhaps because you've signed up to a site which provides mail addresses, knowingly or unknowingly, to spammers) or you've got the type of email address which is easily guessed at. (e.g. spammers will send mail to
[email protected],
[email protected],
[email protected], etc, in the hope that some of the 'guessed' addresses are actually valid).
Actually, there's a third possibility. One of your 'friends' might have signed you up to something 'naughty' on the internet, without your knowledge.
Norton security software seeks to block viruses, trojans, etc. It doesn't deal with spam ('rude' or otherwise). There's no way to completely block spam; some people get thousands of spam messages every day. However, this free software can help with the problem:
http://www.mailwasher.net/