Sending email problem

i am running XP on desktop and laptop with sp2. at home email(outlook express)and internet access work fine. This is through a wireless network and satellite internet access. When i go to a friends place and connect through a cable ethernet connection on broadband i can access the internet and can recieve emails but i cannot send emails . I keep on getting the error code 1503 msg. I use nortons Internet security 2006 and nortona antivirus and these programs present no current problems. I am at a loss as what to do next becasue i dont want to stuff up the current access i allready have at home. Any suggestions would be gratefully accepted