Greetings, I have company's odoo instance on odoo.sh (15 enterprise) where i have outgoing SMTP server setup. Not sure how incoming (support) smtp server is working support@company.com , because it was never setup manually and incoming mail servers are empty.

In helpdesk overview when se setup Email Alias - it says "Create tickets by sending an email to an alias"

When i send email to support email. it sends me automatic response and gives ticket number (ticket reference (#1)), but when i answer on that response from email instead of keeping that number (ticket reference (#1)) it creates new ticket (ticket reference (#1) (#2)). So basically it will escalate with every response.
Is it normal behavior?
Can i fix it somehow?
Is there code that checks if user responding on odoo-side email?

I found helpdesk/models/helpdesk_ticket.py line 474 function that creates new ticket number, but had no luck debugging where does it check if it is response for odoo-side email or not.

Any ideas are welcome, not sure what to try next ...