Amazon S3: Static Web Sites: Custom Domain or Subdomain

Make sure that you follow the S3 DNS bucket naming conventions when creating your bucket.

Then:

1. Enable S3 Website support for the bucket using the AWS Management Console at Properties --> Website

2. Make sure the files in the bucket have public read permissions

3. Try the website using the endpoint listed in the Management Console

4. Setup your CNAME using the listed endpoint (e.g. www.example.com CNAME www.example.com.s3-website-us-east-1.amazonaws.com)

It turns out that to make it work, you cannot just map any arbitrary subdomain to any arbitrary bucket. The fully qualified subdomain name must be the same as the S3 bucket name.

1. Suppose the name of your site is static.mydomain.com. Then you need to create a S3 bucket with that same name, named static.mydomain.com.
2. Once you configure that bucket as a S3 static web site, it will have a URL assigned to it that looks something like http://static.mydomain.com.s3-website-us-east-1.amazonaws.com.
3. Go to your domain host and map your subdomain to the URL from step 2. In enom.com, that meant mapping the host "static" to the address "static.mydomain.com.s3-website-us-east-1.amazonaws.com" as a CNAME record.

Thanks to Uriah and David for suggestions. I eventually got my answer at an Amazon AWS forum.