Apple Mail is the email client I use as it looks good and has a great search function. But it doesn't matter if you use Apple Mail or something else, if you don’t want your every move tracked, you have to prevent your email client from loading external images. On OS X, I use Apple Mail and the way I block external images is with Little Snitch.
The way to do it is to block all connections except the ones you allow.
But for some services you do want to see the external images.
In my case one service for which I do want images though is Basecamp. 37signals finally upgraded their email notifications to html and they look a whole lot better and are arguably functionally better as well – as the presentation of information is clearer.
So how do I get the thumbnails in Basecamp?
If you’re on OS X with Little Snitch and Basecamp, unblock:
If these two don’t work, what you need to do is open the source of the email (in Mail command-option-U). Unfortunately 37signals chose to use Base 64 encoding for the html part (absolutely no need to do so).
You want to copy the part of the document that comes after this:
--mimepart_4b8295ce1ce1d_4f231be02701438a6 Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: Base64 Content-Disposition: inline
and before this:
and then take it to ToastedSpam’s Base64 Decoder and plug it in.
You’ll now have plain html and you just have to search for asset or img in the html. Add those domains to Little Snitch to allow connections in Mail.
If there are any other html emails for which you would like the images, you can use a similar technique to allow their images. Keep in mind most newsletters have a link to allow you to open the email in a browser which is a quicker and easier solution.