First I will thank everyone who helps here. MiaB is a great tool and light weight I guess.
My approach is to run a mail server on different vps and run a web server other vps.
The problem is I have already running my web server and pointing the A record to the vps IP but I am not sure how can I run MiaB without touching that. I have little knowledge about the how the system works.
Can anyone please help?
Domain from namecheap **