How do I mark a Gmail message as high priority?

Google Mail does not provide options to prioritize email based on importance level (low, normal, high). Gmail learns which emails are important to you by evaluating who you send email to frequently and which senders' email you open quickly
The Subject can show importance using something like:
a. ***Important - We need this documentation by the end of the day
b. ***Urgent - We need this documentation by the end of the day
c. ! - We need this documentation by the end of the day
You also have the ability to mark received emails as "important" or with a star for better visibility:
a. Put a check mark in the left box next to a message
b. the More drop down
c. Select Mark as important or Add star

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