PING and TRACERTE can also help you in your issues as well. If you do a PING SMTP.GMAIL.COM and you get no resolve then you know it is a DNS error in your network. If you do a PING and you get a resolve but then timeout, you might have a firewall issue. A TRACERTE (not sure of utility name....sorry) will show you how far you go in connecting to the server. It may stop inside your network or you are getting to the firewall and to an external router but no further. In that case your router isn't forwarding it out to the internet.
Software Zen: delete this;