He did look for domains with MX records in his study
> Mail (2.6% or ~3.5 million)
> Any domain not in any other category, but with MX DNS records (for email), I categorized as Mail. I did not attempt to see if the mail server was working or if delivery was possible. It's possible that many of these domains are not actually used for email, but I've given them the benefit of the doubt.
> Mail (2.6% or ~3.5 million)
> Any domain not in any other category, but with MX DNS records (for email), I categorized as Mail. I did not attempt to see if the mail server was working or if delivery was possible. It's possible that many of these domains are not actually used for email, but I've given them the benefit of the doubt.