But (presumably because it's an older version of OE) Jrtv's mail client DOES have access to a spell checker (even though it's in the wrong language), Chuck.
Since no version of OE actually has a built-in spell checker, I have to assume that Jrtv has a pre-2007 version which make a call upon the spell checker within Microsoft Word. So the obvious thing to try is to open Word and to try to change the spell-checking options from within that program, rather than directly within OE.
Chris