Is this author scanning a list of "top domains" instead of full zone files or a random sample taken from a full collection of zone files It seems plausible tha

Is this author scanning a list of "top domains" instead of full zone files or a random sample taken from a full collection of zone files It seems plausible that domainnames registered to individuals hosting their own email would _not_ likely be in the "top domains" Perhaps this headline could be more accurate if it was something like "Self hosted email among the top 1 million domains continues to steeply decline"