Store Attachment on external directory

For Interaction Templates you have the opportunity to store the attachments in the Navision Database or on an external Directory. I want to store the attachment on an external directory to have the opportunity to mail this attachment at a later moment. When I want to store the attachment it will be stored without the .doc extension of Microsoft Word. Does anybody know how to store this attachment with the doc extenstion. Remember that it is a document with merged fields.

The files located in the external directory are not meant to be accessed directly but only via Navision. Secondly I doubt it stores any files with merged data. It always merges on-the-fly, even when showing attachements from the Interation Log Entry list. Have you tried adding the extension to one of the files and then opened it in Word?