Sometimes, if I just have a quick minute to scan through my email, I will start to read a message and realize that it requires more attention later. Yes, I could flag the message to show its importance, but the most obvious mail attribute to me is unread (bold) and read (not bold).
You can easily mark a message as unread from the Menu Bar. Go to Messages / Mark / As Unread. You can also use the keyboard shortcut Shift-Command-U.
Then when you go back through your mail later when you have more time, the messages you marked as Unread will jump right out at you.
NOTE: Mark as Unread is something I use on the iPhone all the time because on the iPhone I am usually checking my messages really quickly. Mail on the iPhone has a button right in the mail message itself to Mark as Unread.
Shopping online? You can help support Basics4Mac by making your Amazon purchases through this website. Simply click the link below and you will be sent to Amazon.com. Any purchases you make at Amazon by going through this site will give me a small commission. It does not affect the price of the items you buy.