How to 'UPDATE' a ticket instead of 'CREATING' one, with an inbound email?
The scenario is this:
The "UPDATE" function looks for keywords in the body of the email, and not at the subject line.
The following string needs to be included in the email body, as appropriate for the ticket type:
%INCIDENT_ID=<Incident ref number>
%REQUEST_ID=<Call Request ref number>
In order to have the best chance of the end user including this string, it should be included in the email response notification that was configured at Step 2.
This way, when the user replies to the response, their email will include the above string in the body of the email, and it will be processed as an "UPDATE."
See the guide that follows for more details.
ITSM 14.1 Wiki: Choose a Notification Phrase includes an example at the bottom of the page which steps through this scenario.
ITSM 14.1 Wiki: Define a Mailbox is the entry point for defining inbound Email handling.