[aarlo]

We have a special tracking code that figures it out over the email clients' use of HTTP and with some fancy server-side node/mongodb stuff.

[2mur]

Maybe a throttled node.js response on an img on a large image file? edit: Oops I see that staunch beat me to it.

[Udo]

It's still bullshit. Most email clients don't display images by default. The notion that email reading behavior can be tracked with anything resembling reliability is a blatant lie.

[rorrr]

Bullshit. There's not a single major client that executes code from emails.

You might be able to have some <img> link back to your server, but even those are blocked by default.

[FaceKicker]

Are images blocked on hotmail, yahoo, etc. too now? I've only used gmail for the past 5+ years.

Either way though, it wouldn't really produce a random sample, though maybe it would allow somewhat meaningful comparisons between separate email campaigns even if the absolute numbers aren't too meaningful.

[rorrr]

Yeah, all of them block images for emails that come from new contacts.

[OJKoukaz]

They aren't blocked by default in all clients. Check your mom's iPhone, it loads images by default.

[rorrr]

If that's true, it's very dangerous. Imagine somebody finds an iphone image vulnerability, a virus based on it will spread across the whole world in a couple of hours.