Hi @JulianF
Greetings from Community Forum
I understand that there are issues with the email appending to ticket and instead getting created as a new ticket in your helpdesk. For an email to be added as reply to an existing ticket or to be created as a new ticket it follows the threading checks that we have in the backend.
Here is an article for reference on the threading parameters :- Threading parameters and Checks
So unless an email satisfies one of the email markers check and one of the sender email checks, it will be created as a new ticket in your helpdesk.
Could you please check if the above points are satisfied in your case and still it creates a new ticket? If yes, could you share the email headers of the original email and one that got created as a new ticket so we could have this checked?
The below link should help in getting the same:
https://mxtoolbox.com/public/content/emailheaders/
You can drop an email to support@freshdesk.com with the headers and we should be able to check the logs for what caused this in your account. We would request you to help us with recent samples in the last 21 days.
Let me know if you have any follow up questions or concerns with the same.