Install Script Ends At "Please Point Your Domain At Your ipv6 Address"

[Majoraslayer]

Title says it all. The install instructions mention that the script should provide some info that is exported to a file for reference, but instead the script ends with a warning to point my domain at my IPV6 address. I don't have an IPV6 address, as I've disabled IPV6 on my network for security reasons with my VPN. I've successfully set this up previously on another server install with Ubuntu, but I'm not having any luck on a new Debian install. After the script completes, I'm getting a certificate error that seems to be pointing to an invalid internal self-signed certificate using my internal hostname instead of my domain name (according to what Thunderbird is seeing).

Is the script supposed to be pointing the mail server to the correct letsencrypt certificate, or does Debian come with some kind of self-signed certificate I need to delete, and is it failing to do this because of the IPV6 issue?