IMAP supports cleartext, NTLM or MCIS authentication... the first two use your NT password, not real sure how MCIS works, frankly.
The Exchange schema has no entry to store a password so it relies on the NT account info. I don't think there's an alternate mechanism you can use to store a desktop access password unless someone else on the board has a snappy idea. I would think that folks using Eudora would have an NT account to get onto the network anyway so this is probably not an issue.
Jeff Lindborg
Unity Product Architect
Active Voice Corp
jlindborg@activevoice.com