Adding New Ip to A New Subdomain

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

Hello,

I would like to know how to assign new ip to a new subdomain in iredmail. I tried to add domain and created spf and dkim successfully but when i send email it takes the main ip of the server alloted to different virtual domain at initial setup. How can i do it?