Microsoft Outlook looks for a special email header, X-Message-Flag , and if found, will display a message to the user in the message dialog along with a red flag. If you mail client (MUA) permits the creation of custom headers, you can create an X-Message-Flag header and assign some arbitrary text string to it. Only users of Microsoft's Outlook will see the message. Some of the messages are funny, some pro-Linux, some anti-Microsoft, some informative, some just stupid. A few example messages are: Warning: Outlook transmits Viruses! Upgrade to Linux Now! Using Microsoft software might be a security risk. If you can read this, you're too close! Message text blocked: VIOLATION OF US 1201(a)(3) Warning: message not sent with a DRM-Certified client User-Agent. Warning: Your mail program does not comply with RFC 1855. Magic 8-Ball says Outlook Not Good. Outlook : A program designed to spread viri, but it can do mail too. Linux : The choice of a GNU generation. OUTLOO
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