mail delivered locally, but I wanted relayhost delivery

==== Required information ====
- iRedMail version: 0.8.7
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): Mysql
- Linux/BSD distribution name and version: Ubuntu 14.04.1 LTS
- Related log if you're reporting an issue:
====

Hi Mr Zhang,

I have mail server by Our Hosting in Our head office,
and I work at remote site, I make mirror mail server, using iredmail combine with getmail, and It's work now

but if I send email localy domains, it's can't be delivered to our primary mail at head office,

How can I deliver all Incoming mail to our smtp provider ..