Please find the below Steps to modify alarm email message:
- Go to "Administration | Rules & Notifications | Rules"
- Select the rule, clike on "View & Edit" and then on "Rule editor"
- Expand any/all of the severity condition levels and select the "Action" tab
- Click on the "Email Action" (which is a link)
- Click the value column of "mail.message"
- On the pop-up window select the tab "User Defined"
- Here enter the needed email message
- Finally save the changes
The same you can do with other email components like subject, recipient, etc.