Definitely follow fotoguy's advice. Also, make sure your SMTP username matches your POP3 username - it's a common mistake to put "username" in one and "firstname.lastname@example.org" in the other!
Oh - and for future posts in the newbie forum, please chose a more informative subject, like "trouble with SMTP and kmail". We already know your a noob (this is the newbie forum
). More people will be able to respond if they don't have to guess what your question is about .