When you create a new Email Account you need to check Enable Incoming in order to then select a DocType to append to. The description of that field says Append as communication against this DocType (must have fields, "Status", "Subject").
Looking at hooks.py in the apps/frappe shows a line email_append_to = ["Event", "ToDo", "Communication"] to which I added "Warranty Claim" and then it showed up after doing a bench update --patch:
Now I didn’t test this and the question is how you overwrite that array in the hooks.py, probably if you have your own app and have a hooks.py in which you overwrite the array that should work. You may then have to add the fields Status and Subject to the Warranty Claim DocType as custom fields.
I think this points you in the right direction, you will need to do some light coding as far as I see.
We want to import the emails but not all, we want to filter the emails and then append them to specific doctype, for example: opportunity. When searched I found this suggestion