Email templates wouldn't be worth anything if you couldn't include useful information about the ticket, the post and the user in them. You can do so by using "variables". The variables are ALWAYS written in all-uppercase letters, surrounded by square brackets, without spaces, exactly as defined below. The available variables are:
The name of the email recipient.
The username of the email recipient.
The numeric ticket ID
The ticket's title
The full name of the person who posted the ticket / reply
The username of the person who posted the ticket / reply
The post text
A link to the attachment (text and URL), left blank if there is no attachment
The URL of the ticket on your site
Ticket category name
The name of your site
URL of the avatar image of the user who posted the ticket / reply
The origin of the post (e.g. web or email)
The full name of the support staff assigned to the ticket, or the text “Unassigned” when nobody is assigned yet.
The full name of the last person who modified the ticket. This is the same as the [POSTER_NAME] on most email templates. On the assigned ticket email it is the person who assigned the ticket to another member of the support staff.
The only variables available for the
mailgateway-invaliduser key is
The ticket variables ([ID] through [CATNAME] and [ORIGIN]) are only available for the "Akeeba Ticket System - New post notification emails" plugin's Keys.