HTMLBody is supported in all versions of Outlook beginning with Outlook 98. Starting with Outlook 2003, it is considered one of the properties that may trigger a security prompt (depending on the code environment) when code attempts to read value. No prompt occurs when you set its value.
--
Sue Mosher, Outlook MVP
Outlook and Exchange solutions at
http://www.slipstick.com
Author of
Microsoft Outlook Programming: Jumpstart
for Administrators, Power Users, and Developers