NavCIS was one of the first e-mail and forum clients to feature WYSIWYG e-mail in the early 1990s.
For a while, a Macintosh version called 'CompuServe Navigator' was also available, which fulfilled the same function. It ran on MacOS 4.1 up to 7.1, and made it to at least version 3.2 (released sometime in 1994, when it retailed from CompuServe for $99.95). (source:
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