When we meet a person for the first time, we look for signals to determine whether that person is trustworthy. For example, if you are working from home and a stranger knocks on your door. You might look at a camera to decide whether to open the door. If you see a person wearing an Amazon delivery uniform, you’re likely to open the door because that uniform indicates that the person is credible.
If the person knocking at your door isn’t wearing a uniform or any other marks of a corporate entity (materials in their hand, logo shirt/hat), you’ll look for other signals: gender, hair, clothing, posture, body movement. And in a split second, without being conscious of what you’re looking for, you’ll determine whether you will open the door or pretend not to be home.
The same thing happens with writing. When we receive a message, we look for signals about whether the message deserves our attention. If it’s from a person or organization we know, we’re more likely to read it because we already have a relationship with that entity. Messages from unknown people or organizations require more consideration.