OS X Mail includes an importer for Eudora mail. However it will not attempt to integrate attachments into the mailboxes and message status is not preserved.
A better free option is a freeware application called Eudora Mailbox Cleaner. Mail is imported by dragging the entire Eudora data folder onto the top of the application and then selecting whether you'd like to import Mail, Address Books info, Filters, or any combination of the three. Imported messages are placed within a local folder called "Import." Each imported folder will initially appear to be empty until it's been selected and the Mailbox > Reconstruct command run.
For incoming messages attachments are integrated into the mailboxes. Message status is preserved.
- Outgoing messages will lack attachment information.
- Attachments not in the default attachment directory will not be integrated into the mailboxes
- Possible problems with large mail stores--lengthy import times and incomplete imports
Emailchemy is a commercial utility IT Services has successfully used to import large mail stores. It will do a more complete job of integrating attachments compared to Eudora Mailbox Cleaner, as attachments do not necessarily need to be stored in the default attachments directory.
- Message status is not preserved using the standard option to output Mail.app compatible mailboxes. All messages show as unread. An alternate conversion option Emailchemy provides involving a built in IMAP server theoretically resolves this. More information will be posted here as it is known.