It detects the headers of the mail and according to its trained model it blocks the mail and allow only clean mails. This will help to avoidunwanted mails and phishing mails

Phishing is an attempt to steal personal information or break in to online accounts using deceptive emails, messages, ads, or sites that look similar to sites you already use. For example, a phishing email might look like it's from your bank and request private information about your bank account.