how to test with paypal sandbox

i am using a business and a buyer account for paypal sandbox. i am using 216.113.191.*,
173.0.82.*, 66.135.197.*,216.113.169.* as the ip addresses (i think a couple of the ip addresses are old but i dont think that will matter if i have the new ones), and www.sandbox.paypal.com/cgi-bin/websc for the url instead of the real paypal one. when logged into the paypal sandbox accounts, it looks like the money gets transferred between the accounts. my problem is that i receive emails saying
" Hello,
A Paypal notification was refused because the connection to the confirmation server failed."
Does this mean one of the ip addresses is incorrect? did i miss a configuration? or is my hosting company blocking messages? any thoughts on how to get this to work would be appreciated.
Thanks.