how to setup custom domain

I'm trying to setup a domain for sendgrid email verification. When I add the domain I get an error that Unreachable cname target (localhost). Please check app domain target

TL;DR

Developers are trying to set up a custom domain for their Sendgrid email verification. They have already redirected the IP to the domain. However, when attempting to add the domain, they receive an error stating "Unreachable cname target (localhost). Please check app domain target." They are using the self-hosted version of Appwrite. A solution or further steps to resolve this issue are not provided.