Has this worked before? New connection? New ISP?
Lots of times, this is something like a mispelling of the outgoing server name, or using "mail" instead of "SMTP" possibly. Double check your typing, or better yet, have someone else verify your typing! I've looked at something numerous times, only to have someone else immediately spot a typo! Double check with your ISP to verify the outgoing address.
Here's a tip - when you get an error message, copy that message -verbatim- into Google. 95% of the time, or better, you'll find a response that will fix your problem!!
One example:
http://www.experts-exchange.com/Netw..._20834961.html
Best of luck - let me know if you get it going!
Al