OK, well, looks like your SMTP settings are just fine, and obviously, you haven't changed them just recently.
More likely, your firewall is blocking the emails. One quick way would be to simply turn it off, just for a short while. Somewhere, within your Norton Control Panel, there will be a firewall setting, you should be able to turn it off temporarily, and then try sending a few emails.
For the record, there are hardware firewalls and software firewalls. Picture them as exactly that, a ring of fire protecting those on the inside from any nasty creatures on the outside! In a typical setup, say 3 PCs wirelessly sharing a broadband internet connection, there would be 1 hardware firewall provided by the router, and each PC would run its own software firewall. In simple terms, the hardware firewall does the main job of stopping things (hackers) getting in, the software firewall stops things going out (as in rogue applications sending out personal information, or Denial Of Service attacks to company servers). However, the software firewall doesn't always know what is legitimately trying to contact the outside, so we need to tell it. For example, your email client is something you want to pass through the firewall, as you need to send emails. Other applications will also attempt to connect to the internet from your PC to see if there are software/driver updates (Windows, cordless mouse & keyboard, anti-virus software itself). What would normally happen when something tries to connect to the internet, typically at Windows Startup, would be that your firewall would kick-in and say, for example, "Logitech iConnect is trying to connect to the internet...do you wish to allow this?". You would then be given the option to say yes to this, and would not be asked again. You shouldn't really be asked this for email, especially something like Outlook Express.
Paul