Whenever an agent replies to the thread of an already existing ticket from their mailbox, it will be added as a public note on the ticket. 

If the agent sends an email to the support email address as a new thread, it will create a new ticket with the agent as the requestor. 

To append a new email to an existing ticket, include the Ticket ID at the beginning of the Subject line of the ticket in the format, [#{{ticket.id}}].

For example, the agent would have to insert [#1234] to the subject of a new email to append that email into Ticket number 1234.