Emails not receiving from one custom domain to another

Hi,

We have added custom domain @abc.com (default) in O365 and routed the emails as well, everything is going well until i added another custom domain @xyz.com and verified as well but didn't router the emails yet. 

Now @xyz.com users are not receiving emails sent from @abc.com (default), however, @abc.com (default) domain can receive emails sent from @xyz.com domain.

Is it due that both domains are in the same office 365 subscription and i have to perform some additional steps?

Thanks in advance..

Regards,

Amir