Companies track their marketing campaigns in various ways like, in mass mailshots they add tracking images so that they would get more information about the users who have opened and read their marketing message. They collect users' information such as, IP addresses which help them determine the country, and client software which help them determine the type of operating system, etc. Mike Cardwell takes privacy extremely seriously and has developed and published an online email privacy tester so that users can test if their email client software is set to allow tracking through remote-loading images!!!
Check your email client software here - https://emailprivacytester.com/