Depends on what you're tyring to do. The closest I'm able to get is to point UltraEdit at old Eudora Light V3.06 .mbx files. There are some very handy tricks that you can do for finding old emails, archiving, truncating, etc. It would be too cumbersome for routine email manipulation, though, stuff like spellcheck.
That is still the main reason I use Yarn for Dos. Own editor, own spell check, and own mimer/pgp'er - all that is configurable. Yarn is just getting a bit long in the tooth, but having my own editor (even ultraedit) at my disposal for every message is excellent.
>point UltraEdit at old Eudora Light V3.06 .mbx files
Anyone using UltraEdit macros (or others) to manipulate Eudora? I just wrote one to prep huge attachment files for real estate agents (deleting useless or confidential fields). I now suspect that it's possible to entirely automate the process. This thread came to mind.