Frank Saunders MS-MVP IE said:
No. The program was abandoned before they got to that.
Dictionaries used by Windows Mail appear to have a different file format
than the Office dictionaries on which they are based. Do a search on your
system partition for "*.lex" files and you will find four that match up as
to size named "*.lex.bin" in those x86-**** directories with the real long
names. In the absence of information as to file format, there is no way to
even hack a GB dictionary into Windows Mail, short of adding the words you
want (there are lots of them) into the custom user dictionary.
Windows Live Mail is considered the alternative for people who want to add
or use another spelling language. More information is available in various
threads in microsoft.public.windows.live.mail.desktop. Program available on
http://get.live.com. People have added spelling dictionaries for Danish,
Swedish, Italian, Portuguese, and English for GB to Windows Live Mail. In
addition it can be used to access your free Hotmail account.
This is still a big step backwards from what was available in XP and Office
2003. There, any language you added to Office spell checking was
automatically available for use in Outlook Express.
Earle