Eudora actually uses the Apple Keychain Access. Just go to Applications > Utilities > Keychain Access. Once its open, search for a keychain that is named the same as the last part of your email address. For example, if your email address is "joe@earthlink.net", then look for a keychain item named "earthlink.net." Select it and click on Access Control to see which application has access to it. Make sure its Eudora, then under the main tab, click on "Show Passphrase.