Comment Surprised It's Only 2/3rds ... (Score 4, Interesting) 217
Having long ago worked for not-even-close to the largest or most sophisticated marketing emailer (on behalf of Fortune 500 clients) waaaay back in 1999, the use of "spy" pixels (aka beacons, etc.) was de rigueur. So much so that firms couldn't compete without even that very basic tracking functionality in place.
Even assuming that by now a lot of what was once outsourced may have been taken in-house with turnkey emailing solutions, I find it hard to believe that adoption of this technique isn't closer to 100%.