Microsoft Outlook is a popular e-mail program used to send and receive messages. Senders have the ability to "encrypt" an e-mail message so that the message is more secure. However, there seems to be a common problem where the recipient cannot open the encrypted e-mail in his or her own Outlook program. The reason is that the recipient is trying to open the email in "cached exchange mode," which does not allow encrypted e-mails. This problem happens in Outlook 2003.
Open the Outlook program. Go to "Tools" and "e-mail Accounts."
Click "View or change existing e-mail accounts" and "Next."
Click the name of the account you want to change and click "Change."
Clear the box next to "Use Cached Exchange Mode" and click "Next."
Click "OK" and "Finish."
Close Outlook and then reopen it. Open the encrypted e-mail message.