I am setting up a server with contabo and I have it set to two IPs

This is my netplan which I have altered in a attempt to not put myself on blast.

network:  
  version: 2
  ethernets:   # Define an Ethernet interface (eth0 in this case).
    eth0:
      match:     
        macaddress: "01:70:76:77:81:3c"
      addresses:  # Assign multiple IP addresses to the interface.
       - xxx.xx.x.359/21   # Website's IP address (primary).
       - xxx.xx.x.360/21    # Email server's IP address (secondary).

      nameservers:
        addresses:
          - 'xxx.xxx.xx.xx'
          - 'xxx.xxx.xx.xx'
          - 'xxxx:xxxx:xxxx::x:xx'


      set-name: "eth0"

      routes:
       - to: default
         via: 219.69.0.1

       - on-link: true
         to: default
         via: fe80::1

I want mailcow on one ip and the website on the other. I am running wordpress website via nginx. Do you have advice other than how I should run the mail server on a different server? I was going to use the docker container version of mailcow. I have hit a brick wall as I am lost in the sauce. I was woundering if anyone else has attempted to do this.

So to simplify I am running a contabo virtual server with 2 ips running a wordpress site via nginx. One Ip is running the website and the second IP I want for the docker mailcow.