EoN wrote:A 1 px hack like the one you mentioned will be caught by a *LOT*, if not ALL spam filters. Definitely Hotmail, Yahoo, Gmail, Outlook etc will block it, but even more I would imaging. But I'm guessing you already know this!
tgavin wrote:If this were the case, then ANY HTML email with <img> tags would be marked as spam. I think you're referring to embedding the images, which is very bad practice.
Chris Corbyn wrote:EoN is right... 1px image hacks are a bad idea and it's not really something I condone. But for a spam filter to detect if the image is tiny or not it would have to download it which would cause bigger issues. I dare say if you had "width=1 height=1" in the HTML it would start alarm bells ringing though.
But I'm confused by your statement that embedding images is bad practice? Why? It's more bandwidth intensive I know that but it's a good way to deliver such content to end-users with a little more privacy.
tgavin wrote:The 1px img hack isn't the best idea, but for now it's the only one (that I know of anyway). return-receipts just don't work. People want to track their email. They're very fussy about that. However, since this is for opt-in lists it shouldn't be an issue.
As I said before, find me a better tracking solution and I'll gladly use it

In my eyes, I see remote images as worse practise than embedded images - from a viewpoint of privacy. I agree with Chris that now days, remote images would now be considered 'spammier' than embedded images.
Also, even if the emails don't get entirely 'blocked' as spam, you can be 100% sure that the email clients will 'hide' all remote images anyway (unless the end user either clicks 'display' or changes their security settings)
From my perspective I would have imagined that Spam Detectors would see remote images that link back to scripts on servers as a dead giveaway that you're trying to track. Or if you look at 'tracking' from a spam point of view, it is used to determine if this email has reached its recipient, in which case it would be a 'hit', and the spam-sender would know to keep that email on the records forever, and sell it, and so forth.
As far as I know, remote images were blocked by email clients long before embedded ones.
Also - what Chris said about the cheker 'determining' if it's a tracker iamge is a good point. I'm thinking (not sure if this is how it works, but assuming), that it woudlnt be too hard for a spam checker to see that an image is linking back to something that is either a) not an image extension, b) has GET parameters (or even just a url) that look like 'identifiers' of any sort. In fact it would be VERY easy to determine.
tgavin - re your question "find you a better tracking solution". Welcome to 2008!!! 4 years ago I didn't even bother trying to use 1 x 1 tracking images, because it was outdated technology that is the oldest trick in the book. If email clients and spam catchers are getting smarter, tighter & more effective, I hardly think they're going to let such an obvious technique through! Have you even checked how many of your emails get to their recipients? People that "want to track their emails" are going to have to be told that it's at the cost of potentially a *HIGH* percentage of their emails being blocked. That's how it is, love it or leave it.
Hey, I wish there was a way to morally track as well without any privacy issues, let alone spam filters. But I gave in to the fact that there isn't, long ago. So did the last 3-4 companies I worked with.