I have postfix mail server and I can send/receive internet mail(ie. someone@yahoo.com) at Linux box. However, when I use MS-outlook, I can only receive mail and can not send mail out It say: 554 <xxxxxx@yahoo.com>: Recipient address rejected: Relay access denied. I have no problem to use Outlook to send and receive mail to user(s) at the Linux box.
I think I need to get a rid of relay restriction but don't know how.
Could anyone please show me how to solve this problem.