Prioritize content when responding to text-size changes. Not all content is equally important to users. When users choose a larger text size, they want to make the content they care about easier to read; they don’t always want every word on the screen to be larger.
For example, when users choose a large accessibility text size, Mail displays the subject and body of the message in the large size but leaves the less important text—such as the date and the recipient—in a smaller size.