If you've got those ObjectSupportLib blues...

In order to run on a Power Macintosh, the Fat versions of Eudora
require the ObjectSupportLib extension.  This comes with AppleScript
1.1, which is distributed with Power Macintosh models sold in the
United States.

You don't have to install AppleScript, you just have to install
ObjectSupportLib.  To install ObjectSupportLib, dig it out of the
AppleScript 1.1 folder (AppleScript Setup:Apple's Scripting System:RISC
Support:ObjectSupportLib) and drag it onto your system folder.

If you can't find ObjectSupportLib, you'll have to use the non-fat
version of Eudora for now.