Is it possible to reply ticket via email on same ticket id not create new ticket id?

I try to create ticket submit on my web site by zoho desk "Advanced Web Form".

When customer submit ticket (e.g. Ticket id #001), I login to zoho desk and move ticket to department (e.g. move ticket to hardware department).

When sfatt from hardware department reply ticket from zoho desk system it send email reply to customer.

When customer reply ticket (id #001) via email it alway create new ticket id #102 if customer reply via email again it alway create new ticket id #103.

Thank you