It is possible to customize the subject line for alert email notification using the if or switch macros. For example, to set the subject line to “It is a warning!” in the case of a WARNING (notification level), you can set the subject line using the switch macro as follows:
${switch ("${NotificationLevel}","Warning","It is a warning!","Critical","Down","Improved","Up","NA")}
Once implemented, when a warning alert is triggered for the test, the notification in the inbox will have the subject line as “It is a warning!”.
Note: When using the if or switch macro with the email subject, they can only be used with the macros in the Alert Email Macros.
Following are screenshots of the subject and alert notification sent based on the above example:

