Mark has a low end Android phone running Marshmallow. Ever since the last update, any time he uses the voice command feature, he's noticed a message that says it's sending audio to his Gmail account. Leo says it's a normal function of Google voice command. It's just letting him know what account that service is associated with. It's not emailing him, it's just letting him know what account it's using. The phone isn't really doing the dictation, it's sending the voice data to Google servers. It looks like Google is being transparent about it.
Mark should check out google.com/dashboard to see the record of everything he's done with Google.