Configure New Domain with Dedicated IP on Virtualmin/Webmin

My Ubuntu server already hosts 1234.co.za on Virtualmin/Webmin, and that domain now scores a perfect 10/10 on Mail-Tester thanks to its properly tuned DKIM, DMARC and SPF records. I have just registered abcd.co.za and purchased a second public IP that must be reserved exclusively for this new domain’s outbound mail.

What I need from you
• Show me, step by step, how to add abcd.co.za in Virtualmin/Webmin/Postfix so that it sends from its own dedicated IP while the existing domain keeps using its current address.
• Generate and publish the DKIM key, create the SPF and DMARC records, and verify that everything propagates correctly. I do need help with these DNS updates.
• Walk me through all the mail-server tweaks (interface bindings, Postfix transport maps, etc.) required so that each domain always signs and transmits through its assigned IP.
• Confirm success by reaching 10/10 on Mail-Tester for the new domain, just as the first one already does.

Environment details
– Ubuntu (latest LTS)
– Virtualmin/Webmin control panel
– Postfix + Dovecot stack
– Two public IPv4 addresses available

Acceptance criteria
1. abcd.co.za appears as a fully functional virtual server in Virtualmin.
2. Outbound messages from each domain originate solely from their respective IP.
3. DKIM, SPF and DMARC records for abcd.co.za are live and pass all checks.
4. Mail-Tester score reports 10/10 without warnings.

Please focus on clear, reproducible instructions I can follow in the future; remote execution is fine as long as you document every step you take.