TEST:An interesting development of Microsoft Office 2003 is the Information Rights Management (IRM) feature, which allows you to control emails after they have been sent. Microsoft say this:

Creating content with restricted permission
IRM allows an individual author to create a document, workbook, or presentation with restricted permission for specific people who will access the content. Authors use the Permission dialog box (File Permission Do Not Distribute or Permission on the Standard toolbar (toolbar: A bar with buttons and options that you use to carry out commands. To display a toolbar, click Customize on the Tools menu, and then click the Toolbars tab.)) to give users Read and Change access, as well as to set expiration dates for content. For example, Bob can give Sally permission to read a document but not make changes to it. Bob can then give John permission to make changes to the document, as well as allow him to save the document. Bob may also decide to limit both Sally and John's access to this document for 5 days. Authors can remove restricted permission from a document, workbook, or presentation by simply clicking Unrestricted Access on the Permission submenu or by clicking Permission again on the Standard toolbar.

Additionally, administrators for companies can create permission policies that are available in Microsoft Office Word 2003, Microsoft Office Excel 2003, and Microsoft Office PowerPoint 2003, on the Permission submenu and define who can access information and what level of editing or Office capabilities users have for a document, workbook, or presentation. For example, a company administrator might define a policy called “Company Confidential,” which specifies that documents, workbooks, or presentations using that policy can be opened by users inside the company domain only. Up to 20 customized policies can be displayed (in alphabetical order) on the Permission submenu at one time so that individual authors can use them for the content they create.