Accepted Domain Wont Receive Outbound Emails

Hi,

I have had my Exchange up working for a while now.
Recently my boss asked me to create a e-mail account with a different domain name.
Everything worked fine with inbound sending and receiving, outbound sending works fine aswell.

But we noticed that the new accepted domain do not receive any outbound mail.
Can anyone give me a hint on where I should start troubleshooting?

Thanks!