CNAME for tracking domain

Some time ago, tracking domains used the CNAME s.[siteID].hs.eloqua.com but was changed to s.[siteID].t.eloqua.com which is what is captured now in documentation on Knowledge Base. However, I recall that existing domains using the ".hs" CNAME would continue to be supported. Does anyone know if that is still true? We're having problems getting the ELOQUA cookie to drop on our website and are wondering if that could be the issue -- we need to update the CNAME in order for it to resume working.

thanks,

Jeff