Of course the e-mail industry has its own version of this: what constitutes an open? Is viewing an e-mail in the preview pane an open? And if they see it in the preview pane and then open it: is that two opens? Chances are, even your e-mail service provider can't provide this info, which means that if you really need to know, you are going to have to audit it yourself.
About a year ago, my company was working with just such an auditing service, now called Emerging Audit (no relation to Emerging Interest). Emerging Audit places a string of code in the body of an HTML e-mail and can accurately determine information such as the browser type, open rate, unique opens, as well as other information like whether the e-mail was sent with a personalized greeting, if that is what you paid for.
Of course, to use such an auditing service, your list provider has to agree to embed the code and they may not be incentivized to do so since, if the auditing doesn't go well, they might have to make good. On the other hand, threatening to use another list unless it's audited can work in your favor, and lists that feel secure in their ability to deliver might use the fact that they are audited as a sales tool and key differentiator.
The Apprentice Factor
On another topic, I watched with interest this week's "Apprentice." Both teams were challenged to open a bridal shop and get people in the doors to buy discounted gowns. One team (the losing team) printed thousands of flyers and handed them out at Penn Center. They had two customers and profited $1,000. The other team, paid for an e-mail blast at the price of $1,000 to reach 27,000 members of an online bridal resource and magazine. They even forgot to include a phone number in the e-blast, nevertheless, they had a line around the door waiting to get in as a result and profited $12,000, even though their marketing costs proved more expensive than the flyers.
And I thought - 'Doh! Of course. E-mail works.' How else would you get that much mobility from any other marketing channel? Banner Ads? Search? Print? Forgetaboutit! You couldn't even get a TV commercial off the ground in that time period and certainly not with that return on investment. When folks tell me that e-mail is dead, I look at them like they're crazy. Nothing works like e-mail. And if you think differently, YOU'RE FIRED!