Why nginx is not reaching file in azure blob storage?

Here is the minimal reproducible sample

configmap.yaml

apiVersion: v1
kind: ConfigMap 
metadata: 
  name: nginx-conf 
data: 
default: |     
  server {
       server_name myserver.com;
       location /read/ {
       proxy_pass https://myaccount.blob.core.windows.net/mycontainer/file.txt;
       }
     }

In my deployment file, I am mounting the configmap as volume as:

  containers:
    - name: nginx
      image: nginx
      imagePullPolicy: IfNotPresent
      ports:
        - containerPort: 80
          name: http
      volumeMounts:
        - name: nginx-config
          mountPath: /etc/nginx/site-enabled/default
          subPath: default
  volumes:
  - name: nginx-config
    configMap:
      name: nginx-config

After deployment an API call looks:

curl https://myserver.com/read

as a response to getting

{"error":"Not found","status":404}

The azure blob data ist accessible for reading. A pure API call via curl on https://myaccount.blob.core.windows.net/mycontainer/file.txt; is successfully done.