ProtonMail's Lydia Pang explained in a blog post that the company believes "reading emails should be as private as our end-to-end encryption makes sending them."
"Today, we're happy to introduce enhanced tracking protection, a feature that will provide an additional layer of privacy to your inbox. Now you can read your emails without letting advertisers watch you, build a profile on you, or serve you ads based on your mail activity," Pang said.
"By default, ProtonMail on the web now protects your privacy by: Blocking tracking pixels commonly found in newsletters and promotional emails, preventing senders from spying on your mail. Hiding your IP address from third parties, so your location remains private. With enhanced tracking protection, you can continue to use your ProtonMail address to subscribe to newsletters and register for online accounts everywhere while enjoying a better, more private email-reading experience."
The company said about 40% of emails sent and received daily are tracked and that email tracking has increased in recent years.
Companies are able to track emails by embedding pixels in the emails sent to you. The pixels log details about your activity, and ProtonMail said every time you open an email with spy pixels in them, it collects information like when you opened it, how many times you opened it, your location and your IP address.
"The gathered data is sent to the email sender, all without your consent. Email trackers can sometimes even expose your information to third parties, allowing them to track you across the web and connect your online activity to your email address, further shaping your invisible online profile," Pang explained.
"The feature is enabled by default on our web app, so you can enjoy peace of mind knowing that your emails are always protected."
ProtonMail has become well-known as one of the most privacy-focused email services available but faced backlash in September after it revealed it can be "forced to collect information on accounts belonging to users under Swiss criminal investigation."