From MXC Software:
This easy-to-use software secures your files, e-mails, instant messages, and backup data with strong encryption and a digital signature. The software is integrated with the Windows shell; creates its own X.509 digital certificates; signs and encrypts files, folders, and e-mails; verifies digital signatures; wipes files, folders, and free disk space; secures instant messages; creates and extractes certificate-protected archive files, password-protected self-extracting archive files, and regular ZIP files; and has a secure text editor. Many e-mail clients are supported, including Microsoft Outlook, Microsoft Outlook Express, Yahoo Mail, Hotmail, Juno Mail, Lycos Mail, and Eudora. Also, e-mail-content formats including text, RTF, and HTML are supported.