sending the mail to any account outside the domain

hi ll
I tried to send mail using asp.net and vb.net and it works fine and I can send and receive main with in the domain

but I have the following error when I try to send mail outside the domain or to hotmail account
is there any settings should I make in the exchange ? or in SMTP

please see the attached file

I don't see an attached file but more than likely your error is not with your code rather with the setup of your mailserver. If it sends to one user(in domain) but not another(outside the domain) then the code has done all it has to do..the rest is left to the mail server.