I wish gmail would stop changing my settings.

But that request will be made when the mail arrives at Google, not when the user reads it. Thus it doesn't actually tell them anything useful other than it's a valid address (and Google might be fetching the images for invalid addresses just to defeat even this.)

Thanks OP for bubbling this up. These types of scenarios are why i run Little Snitch on the Mac. Haven't tried their competitors, but if you dislike this marketing/tracking activity it's worth a test drive. Otherwise stick to a plain text only email client like Pine ;-)

(Bolding mine)
According to the article, the request is made when the email is opened.

That's actually a good point. So the user will still be identified, but perhaps that's all. And it seems like that might happen anyway, regardless of the image load setting I posted above, if Google is precaching images from incoming mail.

I don't know who is right here; the article linked above doesn't explicitly say when the request to load the external content is made. At first glance, it doesn't make sense for Google to preload all external content, so the latter approach (loading it when the email is opened -- which might never happen) makes the most sense. On the other hand, Google could use this to speed up their email interface, in which case they could choose to preload some content (such as static images) when the email arrives.

There are 1,000 ways that Google could implement this, and it seems that marketers are scrambling to figure out exactly what their hits really mean.

The article mentions "The Google server that temporarily stores the image contacts the Web address where the image is hosted only after a user opens the message," and that this was confirmed by third-party testing, where "Google servers didn't download the images until after he opened the Gmail message and viewed the remote content."

Doesn't that indicate third-party content is not pre-fetched when the email arrives at Google?

It does, and as I said a dozen or more posts ago, that is exactly what is happening.

The caching part of this change happened over a week ago, so the implications have been extensively tested and are well understood at this time.

The IP is useful in determining geographic location, I'm guessing?

So if Google caches the image, Google can now track who is opening emails, and they, not the advertiser, now have the location info? Smart.

Whoops, I was referring to the blog article mentioned by docbert in post 14, not the article linked in the OP, which I hadn't even read. Mea culpa! At least that point is clear now.

Well, Google knew it always anyways. If you login/open emails via GMail, they already have your IP. This just means sender of an email won't get that info, which isn't necessarily a bad thing.