The Mudcat Café TM
Thread #140043   Message #3217136
Posted By: treewind
02-Sep-11 - 12:17 PM
Thread Name: Tech: Senders tell if I have opened an email?
Subject: RE: Tech: Senders tell if I have opened an email?
If you receive an HTML email it's easy for the email to notify the sender. The standard technique is for the email to fetch a 1 pixel transparent GIF file (completely invisible) from their web server. The server will know when the GIF is fetched, and furthermore if they have your email on a database with a unique id, the gif will have been fetched with a URL like this:

http://www.nastyspammer.com/1pixel.gif?id=1287623450129

Where "1287623450129" is your unique id which the server will log and thus they will know who has opened the email.

Getting your mailer not to display embedded images or even not to display any HTML message is an effective but drastic protection against that particular method.