You may not realize it, but the majority of emails you receive from companies you are subscribed to are placing tracking pixels on their newsletters, updates, and notifications.
Tracking pixels are not exclusive to emails. Almost all of the websites you visit will have some sore of tracking pixel that can collect data on online traffic and user activity. Tracking pixels are similar to cookies which collect user data, store it, and attempt to tailor future information towards your interests.
Tracking pixels are tiny 1X1 pixels often camouflaged into the background of the email that collects information about you.
If you open an email that contains a tracking pixel (which is extremely common), that pixel can know:
This is the type of data that marketing specialists want to collect on you so that they can tailor their future campaigns around your interests, high traffic times, and attention span which will ultimately gain more traction for their company or organization.
These analytics are useful for marketing purposes, but arguably they are also an invasive privacy concern for the recipients of these emails.
In North America, there are no regulations or restrictions around pixel trackers on emails, however, in some places such as Europe, consent is needed for them. This can be tricky though as many organizations and companies will make this an automated consent when someone signs up for their email subscription.
One thing you can do is add a pixel blocking plug-in to your browser such as PixelBlock or Trocker, but keep in mind that some tracking pixels will probably still slip through.
Another thing you could do is unsubscribe from organizations that bring little value to you. If you can reduce the amount of emails you receive, essentially, less information can be collected from you.