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We're trying to convert a user's email mailbox from Apple Mail to Outlook 2010.

We copied the files off the mac, and they are mostly directories that end in .mbox and contain a folder called Messages containing .emlx files.

The .mbox extension on the folders initially made me think that these messages were in the mbox format, but after some research I found that the mbox format is actually a single file, so that rules out it being in that format.

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up vote 1 down vote accepted

The vengefulcow site's code is nice, but needs a slight modification if you're messing with newer OSX versions and imap mailboxes, here's a unified diff:

$ diff -u emlx2mbox/emlx2mbox.rb emlx2mbox-works/emlx2mbox.rb
--- emlx2mbox/emlx2mbox.rb      2006-12-13 12:02:41.000000000 -0500
+++ emlx2mbox-works/emlx2mbox.rb        2014-02-16 01:28:38.775293976 -0500
@@ -56,7 +56,7 @@
     # Compile messages in mbox directories.
     mbox_dirs = Dir.entries(source_dir).find_all do |entry|"#{source_dir}/#{entry}") and
-      (entry[-5..-1] == ".mbox")
+      (entry[-9..-1] == ".imapmbox")
     end #find_all
     mbox_dirs.each do |dir|
@@ -68,7 +68,7 @@
     subdirs = Dir.entries(source_dir).find_all do |entry|"#{source_dir}/#{entry}") and
       entry[0, 1] != "." and
-      entry[-5..-1] != ".mbox"
+      entry[-9..-1] != ".imapmbox"
     end #do
     subdirs.each do |dir|
       self.convert_mailboxes("#{source_dir}/#{dir}", "#{dest_dir}/#{dir}")
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You can find a description of the format based on an reengineering effort here:

It has three parts:

  1. The length of part 2, in bytes
  2. The message itself
  3. Message metadata (XML Property List)
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There was a question on Stack Overflow where the answer linked to a program to convert to mbox format.

It appears to be proprietary and therefore not well documented in the public domain.

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But the format doesn't have a name? – leeand00 Jun 29 '12 at 19:08
Well I think it's just called EMLX – conorgriffin Jun 30 '12 at 8:10

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