Several people have asked whether there’s a way to create a Gmail message with a high importance alert, similar to the feature found in Microsoft Outlook.
Gmail does not contain a high importance button. There is an easy workaround to let your recipient know that your email contains important information.
Create a custom subject line
Use the subject line in the email as the high importance identifier when creating your email message.
The recipient of your email will see:
Using stars or exclamation points before the subject title will help your reader quickly spot important email.