Given their vast amounts of information about mail, might their spam filter work by only examining the header? That is, of course, still 'reading' mail - though

Given their vast amounts of information about mail, might their spam filter work by only examining the header? That is, of course, still 'reading' mail - though it may be an acceptable trade off for privacy minded people. And, if it's being interpreted by a machine, does that really count as reading?