You must migrate your email from Apple Mail to Thunderbird because:

1. You are poor and/or lazy and haven’t upgraded to “Leopard” Mac OS 10.5, AND
2. You’ve decided you cannot live without RSS feeds delivered as email

Transferring email from Mail to Thunderbird seems like a basic, straight-forward thing to do. Unfortunately however, it was made as difficult as possible. You’d think Thunderbird would provide support for importing email from Apple Mail, and you’d definitely think Apple Mail would provide support for exporting. In both cases you would be wrong. Instead, you have to do some hodgepodge tasks patched together from disjointed sites across the internet. So, this post collects those tasks into 1 location.

OK, really it’s not that bad. In short, here’s what you do:

RTFA: http://www.macosxhints.com/article.php?story=20051…

the idea is to merge the .emlx files into an mbox file, and copy that to where Thunderbird can see it.

The elaborated version of this is: In Tiger, you convert Apple Mail 2.1 to Thunderbird 2.0.0.16 by:

1. Locate where Mail stores your email on your computer.
   • Most likely your email is stored in the ~/Library/Mail/ folder branched off your home User folder. Open this Folder in Finder.
   • The mailboxes you see in the Mail GUI are stored as subdirectories of two folders in ~/Library/Mail/
   • Default Folders: A folder named with the type of account (i.e., “POP-” or “IMAP-”) followed by your Mail account name (e.g. ~/Library/Mail/POP-person@examplesmtp.com/) holds the default folders for the account like the Inbox, Sent, Drafts, etc
   • Custom Folders: A folder named “Mailboxes” (i.e., ~/Library/Mail/Mailboxes) holds the folders that you have created to store your email in groups.
   • Ultimately, you are looking for directories that are named like your mailboxes in Mail.app, but that have an “.mbox” tacked on the end (e.g., ~/Library/Mail/POP-person@examplesmtp.com/Inbox.mbox/)
     • Each .mbox directory will have 2 items: “info.plist” and a directory, “Messages/”
     • Inside the Messages/ subdirectory are the emails stored in that mailbox. The emails are stored as numbered files with “.emlx” extensions.
2. Download the mlx to mbox utility (click here). This will convert the emails from .emlx files to a single “mbox” file per mailbox which can be manually imported into Thunderbird.
   • RTFA: http://www.cosmicsoft.net/emlxconvert.html
     

     emlx to mbox Converter

     In Mac OS X 10.4 “Tiger”, the default message format for Mail messages changed from the Apple custom mbox-package format to the new emlx format (where messages are stored in individual files for Spotlight indexing). However, if you need to recover from a hard drive crash, it’s almost impossible to recover your mail messages easily since Mail won’t import emlx files and you can’t add them to your mailboxes any other way.

     This tool will convert your individual emlx mail files (found in ~/Library/Mail/) to the old mbox format, used by almost every UNIX/Linux mail client and recognized by many more.

   • Once you’ve downloaded the emlxconvert.dmg disk image, mount it and launch the installation package
   • Follow the instructions to install the coverter
3. Convert your email stored for Apple Mail into a format readable by Thunderbird
   1. Launch the newly installed emlx to mbox Converter from your Applications folder
   2. A dialogue box will appear with a large empty window
   3. For each .mbox directory in your ~/Library/Mail/Mailboxes/ and ~/Library/Mail/*-accountName/ directories, convert the individual emails into a single file per mailbox:
      1. Navigate to the mailbox’s .mbox/Messages/ directory
      2. Select all the .emlx files
      3. Drag all the .emlx files into the empty window of the emlx conversion tool’s dialogue box
      4. If you had a lot of emails (many .emlx files), it may take a few seconds for the files to appear after you have dropped them into the empty window of the emlx to mbox converter
      5. When the files show in the Converter’s window, click the “Save mbox …” button
      6. Save the emails bundled together as a mbox mailbox file. The Converter will create temporary files that you will modify later, so you can save this file anywhere, like the Desktop
4. Finish the conversion: Name each mailbox for Thunderbird
   1. The .emlx email files are now saved as a single file that represents the mailbox that stores them. Each group of emails you converted will have its own directory with the name you gave it when you saved the mbox in the Converter. Inside each directory is a file named only “mbox” with no extension. Locate this file for each mailbox you converted with the emlx Converter
   2. Rename each mbox file according to the name you want the mailbox to have in Thunderbird. Do not add any extension to this file and fully delete the word mbox (e.g., if I wanted a mailbox named “Projects” to show up in Thunderbird, I would rename “~/Desktop/Projects.mbox/mbox” to “~/Desktop/Projects.mbox/Projects”)
5. Put the new mailbox files in a place where Thunderbird can see them
   1. Find where your Thunderbird installation keeps its “Local Folders” directory. The default location is “~/Library/Thunderbird/Profiles/{RandomString}/Mail/Local Folders”
   2. Move all the renamed mbox files into the Local Folders directory
6. Launch or restart Thunderbird. Your mailboxes should be waiting there for you!
7. The first time you view each newly imported mailbox, it will pause for a while to load the messages (this only happens once)
8. The imported emails will appear to be unread. Right-click on the mailbox name and select “Mark Folder Read” from the pop-up menu.
9. There remains one kink in the import: Some messages will have bizarre values for the Sender column and no subject, no message, or something of the like. Luckily, good macosxhints.com came to the rescue on that one:

   RTFA: http://www.macosxhints.com/article.php?story=20051…

   This is easily fixed, though:

   1. Open Thunderbird and view the offending mail folder.
   2. Sort the view by date ascending and scroll to the top.
   3. Check for messages with no subject or date and note the dodgy sender names.
   4. In a Finder window, browse to the location of the mbox file ~/Library -> Thunderbird -> Profiles -> random_dir -> Mail -> Local Folders/, and open it in a text editor. Keep Thunderbird open if you need to refer to it.
   5. For each of the dodgy sender names, do a search for the word From with the name after it, e.g. in this case: From Monday. When you find the text, make sure that it is actually part of the message content.
   6. Add a > in front of the From, e.g. >From Monday — don’t worry, this is the standard way to do it in an mbox file; it won’t show up when you view the message in Thunderbird.
   7. Save the mbox file.
   8. Close Thunderbird.
   9. Delete the .msf file that Thunderbird created for the mbox in the same directory and has the same name, but with .msf — don’t worry, it’s a metadata file that Thunderbird will rebuild next time.
   10. Start Thunderbird again and view the folder and make sure all those partial messages are gone, and the original ones are complete.

FYI: You can set up RSS feeds in Thunderbird easily by adding a new account under Tools->Account Settings. Check out the Mozilla documentation on RSS Feeds in Thunderbird: http://kb.mozillazine.org/Thunderbird_:_FAQs_:_RSS_Basics.

This howto should work for a while on Thunderbird’s end, but who the heck knows with Apple Mail. This is certainly only relevant to Mac OS 10.4 “Tiger.” If you use Apple Mail in Leopard, you don’t have to go through this tomfoolery to read RSS.