What are the Ways to Avoid Email Tracking using Mail?

Read KATE MURPHY's article in today's New York Times - "Ways to Avoid Email Tracking".

I want to do this, but the article was not specific enough to Mail to explain how to do what she suggests in Mail preferences. (see text from article below)

Any hints from people here?

Thanx

"

There are some things you can do to avoid having your email activity monitored. Perhaps the easiest defense is to adjust the settings of your email program so there is no image rendering.

It used to be set that way by default but last year, in a boon to marketers, Gmail made the setting an opt-out feature and many other email providers followed suit. Disabling images will sift and block images from incoming emails, including those tiny, pixel-size tracking bugs. You can click on the missing images you want to see and which ones you don’t."