The scripts generated by the builder for double opt-in ultimately generate a POST action to api.maropost.com, but unfortunately this domain has been added to the block list of some ad blockers, which prevents end-users from subscribing.
As part of onboarding and domain configuration, marketing cloud users already setup a CNAME to use for links, and this ends pointing to the exact same IP as api.maropost.com.
Please allow us to use our links CNAME as the target for the POST from these generated scripts, rather than api.maropost.com. This will help work around any adblock blocklist problems now and in the future