3. The method of claim 1 , wherein the response to the query provided by the electronic mail client application comprises a previewer class identifier for identifying the previewer for the document type of the attached document.
3. The method of claim 1 , wherein the response to the query provided by the electronic mail client application comprises a previewer class identifier for identifying the previewer for the document type of the attached document. 4. The method of claim 3 , wherein the preview handler identifies the previewer for the document type of the attached document from the plurality of separately executable previewers by searching contents of a registry.