Processing Answers to emails sent by the system

I'm building a ticketsystem which creates tickets from incoming email automatically. The workflow look's like this:

1. User send's a email to support@yourname.xyz
2. The System creates a new ticket
3. A Team member answers to the ticket via a Dashboard
4. The User get a notification with the answer per email

Now I wan't to give the user the option to answer the ticket by reply to the email from step 4. But how can I assing the reply to a ticket?

Sometimes I saw solutions where the ticket id is stored in the header. The subject looks then like [#12345] Your Request But is there a better way to store the ticket id so the user can't see it? When I set a header variable on the email sent in Step 4, the varibale won't be included in the reply from the user.

Dose anyone have a soulution for this problem?

instead of prefixing the ticket ID to the 'Subject' field, create a new field in your out-bound mail. Just as you create a 'SendTo' field, also create a 'TicketID' field. This makes the value hidden unless the recipient looks in the mail's headers.

this will then also make it easier to search for replies by the ticket number.

I think I've understood your question, but if not, please clarify.