Mail Server Configuration Issue

Hi Team, I used the install script from the email I received from Carbonio to install the repo—disabled ipv6, set the hostname in the hosts file. Use the official script found here to install it. I believe everything went smoothly.

I can log in to the admin page and webmail. When I try to send an email i get an error message in red on the bottom right of the screen that says Something went wrong please try again.

I am using Ubuntu 22.04 LTS. I don't have a public IP to the VM. The server is behind my firewall with port forwarding. I can access the webmail portal from the internet with no issue. My A, MX, SPF and Dmarc records are set up.

Can anybody provide some assistance or point me in the right direction please?

Thanks.