Currently ProtonMail leans heavily on one of the most widely used open source spam filtering technologies on the internet. We are working on developing more complex algorithms and machine learning to ensure the emails you want to see are delivered to your inbox, and the one’s you do not want to see are sent directly to your spam filter.
Unfortunately at this time there will be mistakes in our spam filtering. These are some things you may see:
- Messages you are expecting to see in your inbox are delivered to your spam folder.
- Messages from people in your contacts.
- Replies to messages you sent.
- Messages from people you have given your email address to.
- Messages you expect to be delivered to the spam folder are being delivered to your inbox.
- Advertisements that you did not request.
- Advertisements that you no longer wish to receive.
To better customize your spam filtering, ProtonMail provides a Whitelist and Blacklist spam feature that allows you to specifically mark email addresses as spam or not spam. You can learn more about how to filter your emails here: https://protonmail.com/support/knowledge-base/spam-filtering/.