Conditional Formatting allows you to customize how different messages appear in your Inbox. The message list based will show messages differently  based on criteria that you set. By default, conditional formatting makes unread messages bold.

By adding your own customizations, you can highlight the messages that are most important to you.

For example, when you are at work, you might want to separate and distinguish emails which have been sent from your boss, manager or supervisor.

For that reason you might want to set these messages to appear larger than others in your Inbox.

To set up Conditional Formatting from your Inbox, go to the View tab,then click View Settings, and then click Conditional Formatting. 

Creating a new rule

Click Add to create a conditional formatting rule. You can name it whatever you like.

Next, click "Font" to choose how you want the text to appear in the message list. For important messages I tend to choose a red color and a larger, bold font.

The next bit is important. It defines the condition for which the emails will be highlighted. In this example, I will use the condition "From"

To do this, click "Condition" to create the conditional formatting for mail where the "From" line contains people's names/emails from my contact list.

You set various rules/conditions depends on your requirements ... Once you've finished formatting the condition you can click "OK" to save it.