I had been putting off upgrading from Snow Leapord (10.6.8) due to the fact that like others posting here my long time favorite email client Eudora will no longer work on any newer versions of the Mac OS.
Eudora Mailbox Cleaner looked promising but it only runs on PowerPC computers running Rosetta. I finally dug into it yesterday and found a pretty slick program called Emailchemy. It's a virtual swiss army knife for converting from and to most of the popular email programs. It's $29.95.
The documentation is fairly sparse and not as detailed as I'd like but for the most part it worked well. The dates of the emails came through, attachments were there, everything in Eudora was moved to Mail. The only thing is I did end up going through viewing all my mailboxes in Eudora and comparing the count of messages to what was converted in Mail. There were a few emails in some mailboxes that for some reason did not transfer. I just forwarded those messages from Eudora and filed them in Mail.
Some of the steps I took:
1. Backed up my entire drive with SuperDuper.
2. Went through my old emails. I had many emails that I really didn't need to save.
(Sorting by sender in Eudora was a big help in finding messages that needed to go.)
3. Re-file or made new mailboxes as I was sorting through the messages.
4. Option-click on the mail count/size in the bottom left panel of Eudora to compact the mailboxes.
5. Made a copy of my Mail and Mail Download folders that are in /Users/user name/Library/
6. Using Emailchemy I started the conversion.
a. Pointed to my Eudora folder in Documents.
b. Choose Export to Mail 1.0
c. From Mail choose File/Import mail.
7. Compared email counts between Eudora and Mail and forwarded to myself messages from Eudora that were missing.
8. Checked dates and attachments.
Emailchemy recommends using the included imap server as opposed to exporting and importing. For whatever reason I could never get this to work despite making sure I had all the ports and settings as mentioned.
I came across an article from 2011 on Tidbits that was the most thorough discussion of this issue after I did the conversion. Although a little dated you may want to ceck it out here.
Glenn Grafton
glenn@graftonpiano.com