While some Ticket types (e.g. Incidents/Requests) can be updated through the Email Interface,on some other types I get the error message:
AHD58040:Updates are not allowed for this table through Email Interface
The definition of which Ticket types can be updated through the Email Interface is specified in the file text_api.cfg. Search that file for this section:
and make sure, the appropriate variable is set to "YES".
Changes in this file require you to restart the Service Desk Manager service.