Update u_e-dovecot-vmail-volume.md

Included the process to move the vmail folder.

docs/u_e-dovecot-vmail-volume.md

@@ -8,3 +8,12 @@ volumes:
       device: /data/mailcow/vmail
       o: bind
 ```
+
+The process to move the vmail folder is:
+Locate the current vmail folder: `docker volume inspect mailcowdockerized_vmail-vol-1` 
+Copy the `_data` folder to the new folder using `cp -a`
+Stop Mailcow by executing (from the Mailcow root folder) `docker-compose down`
+Create the file `docker-compose.override.yml`
+Delete the current vmail folder: `docker volume rm mailcowdockerized_vmail-vol-1`
+Start Mailcow by executing (from the Mailcow root folder) `docker-compose up -d`
+