We want to update Zendesk via email from a system that hasn't received an email from Zendesk.
Questions:
1) Does that require the ID code which looks like "L66B03-3PEVR" rather than only the Ticket #?
2) If so, can we get that ID code from the API? I've looked at the fields and can't find it:
https://developer.zendesk.com/api-reference/ticketing/tickets/ticket_fields…
To update a ticket via email, are we required to use the unique ID code, such as: help+idL66B03-3ZEVR@supportstore.zendesk.com?
Or, is it possible to update the ticket using the Ticket # such as: help+id12345@supportstore.zendesk.com
We did try using the Ticket # and it failed.
IF the unique ID code is required, how could we obtain that without actually receiving an email from Zendesk? Can we retrieve that ID code from the API?

We match an incoming email message to the ticket when we detect that the encoded ID is present in the email body. So that's where you'd include the encoded ID.