I add a CNAME for example1 and example2 to route to my domain however I get site not found error.
The only way I was able to fix it was to add the example1 and example2 into my domain settings however this is not scalable for potentially 1000s of external domains.
Do you have any advice on whether this is possible to achieve through Netlify?
@alexcdev, that is not currently possible as they rely on all domains to be registered within the Netlify proxy first, which can only be done by adding it as a production alias using their DNS. This limitation means that non-production deployments won’t be able to benefit from this as only basic branch-level domain controls are available.
Domains also need to point to Netlify DNS to enable Let’s Encrypt TLS certificate provisioning, which cannot be done without Netlify’s DNS controlling the production alias(es), as they explicitly use DNS for this process.
I’d recommend taking a look at this support guide that recommends solutions for your use case:
The recommended method and easiest way to configure this would be to use wildcard subdomains with the pattern example1.blog.com, rather than blog.example1.com. Once you give that a read let us know if you have any additional questions.