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.

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

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

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.