Workflow API allows to run some code when receiving a new email but not when associating manually one email in the web interface

The Workflow API allows to run some code when receiving a new email but not when associating manually one email in the web interface. The function handleNewEmail allows me to fill automatically custom fields with values from LDAP. But when I want to associate an email in the web interface and create a new ticket, no functions in the API is called, so I cannot fill the values with the values from the new associated emails.

Is there a way to add this ?