This update resolves the 'Persistent Mail Browser Link,' 'Cache Bypass,' and 'Malformed E-mail Header' security vulnerabilities in Outlook Express. Download now to prevent a malicious user from reading e-mails and files on your computer, or using your computer to send damaging e-mails to others. These vulnerabilities do not give a malicious user the ability to add, change, or delete files on your computer. This update resolves the vulnerabilities in Outlook Express 4.01 Service Pack 2 (SP2) and Outlook Express 5.01 only. Computers running Outlook Express 5.5 are not vulnerable to this issue. Outlook Express 5.5 includes this update.