Converting between mailbox formats
==================================

If you want a transparent migration, the biggest problem is preserving message
UIDs. See <Migration.txt> for the problems this may cause. If you do the
conversion with dsync, it preserves the UIDs.

dsync
-----

With dsync you can convert between any two mailbox formats that Dovecot
supports. As much of the mailbox state is preserved as possible. Typically it's
everything. See <Tools.Dsync.txt> for full documentation, here are only a
couple of examples:

 * mbox -> maildir migration. Set 'mail_location=maildir:~/Maildir' and run
   'dsync -u username mirror mbox:~/mail:INBOX=/var/mail/username'
 * maildir -> mdbox migration. Set 'mail_location=mdbox:~/mdbox' and run 'dsync
   -u username mirror maildir:~/Maildir'
 * maildir -> sdbox migration. Set 'mail_location=sdbox:~/sdbox' and run 'dsync
   -u username mirror maildir:~/Maildir'

If you can successfully use dsync, you can skip the rest of this page.

Converting from mbox to Maildir
-------------------------------

 * mb2md.pl with Dovecot modifications [http://dovecot.org/tools/mb2md.pl] can
   convert mails, preserving UIDs and keywords.
    * See also [attachment:migrateuser.sh script to drive the full migration
      for a user].
       * This script requires patched 'mailutil' that supports Maildir. One
         working 'mailutil' binary is RHEL4 PINE RPM
         [http://dag.wieers.com/rpm/packages/pine/pine-4.64-3.el4.rf.i386.rpm]
         from the DAG RPM Repository [http://dag.wieers.com/rpm/]. You could
         also patch any version of pine/c-client and patch it with the Maildir
         patches from
         http://staff.washington.edu/chappa/pine/info/maildir.html.
 * mb2md.py [http://dovecot.org/list/dovecot/2008-March/029736.html] can
   convert also message UIDs.
 * Yet another way to fix the UIDL migration problem. If you can generate an
   uildlist ("messagenumber uidl" pairs), use my new -U uidllist option to
   inject X-UILD: headers in the converted Maildir-file. The modified mb2md
   script is avalable here:mb2md.xuidl.pl.gz
   [http://www.chaos.dk/~sch/mb2md.xuidl/mb2md.xuidl.pl.gz]. I used this to
   convert a cucipop installation to dovecot. pop3_reuse_xuidl=yes will do the
   rest./-- <SoerenSchroeder.txt> 2009-02-13/

Check also the *User-Contributed Maildir Support* section on the qmail
community site [http://www.qmail.org/top.html#usersoft] for more choices.

Example (user's mail in '~someuser/mail' and INBOX in '/var/mail/someuser'):

---%<-------------------------------------------------------------------------
cd ~someuser
mb2md-3.20.pl -s mail -R
mb2md-3.20.pl -m -s /var/mail/someuser
mv mail mail.old
---%<-------------------------------------------------------------------------

Now the mail will be in '~someuser/Maildir'. Do not forget to migrate the
subscriptions as well, otherwise the new maildir will seem to have only an
inbox when viewed through a mail client that supports them. This can be as
simple as copying the old '~someuser/mail/.subscriptions' file to
'~someuser/Maildir/subscriptions' (warning: I have not tested this extensively,
my subscription list and folder hierarchy was very simplistic).

Hierarchy separator change
--------------------------

The default hierarchy separator with Maildir is '.' instead of '/' which is
common with mboxes. To keep the migration transparent to users, you can keep
the '/' separator by using <namespaces> [Namespaces.txt]. In any case you need
to replace the '/' with '.' in the subscriptions file:

 * ---%<----------------------------------------------------------------------
   sed 's:/:.:g' subscriptions > subscriptions.new
   mv subscriptions.new subscriptions
   ---%<----------------------------------------------------------------------

UW-IMAP's subscriptions file is in '~/.mailboxlist'. Dovecot's mbox
subscriptions is in '<mbox root dir>/.subscriptions'. Dovecot's Maildir
subscriptions is in '<maildir root>/subscriptions'.

Also if you're migrating from UW-IMAP, you probably had "mail/" prefixes in the
mailbox names. You can again use <namespaces> [Namespaces.txt] to let clients
use the prefix, or you can tell your users to remove the namespace prefix from
their clients and change the subscriptions file:

---%<-------------------------------------------------------------------------
sed 's/^mail\.//' subscriptions > subscriptions.new
mv subscriptions.new subscriptions
---%<-------------------------------------------------------------------------

Note that because Maildir uses '.' as the hierarchy separator in filesystem,
it's not possible to have mailbox names containing '.' characters, even if you
changed the separator in namespaces. If you really want to have dots, the only
way to do this is by modifying the filesystem separator in 'MAILDIR_FS_SEP' and
'MAILDIR_FS_SEP_S' defines in 'src/lib-storage/index/maildir/maildir-storage.h'
file in the sources.  Do not be tempted to change 'MAILDIR_FS_SEP' et al to
'/'; it won't work.

Converting from Maildir to mbox
-------------------------------

This is especially helpful if you want to archive your mail to a single file
for storage on a CD, a PC, etc. But it can also be helpful if you want to use
<mbox> [MailboxFormat.mbox.txt] with Dovecot.

Use the reformail program that comes with maildrop
[http://www.courier-mta.org/maildrop/]. You can also use the formail program
that comes with procmail [http://www.procmail.org/]. Here is a simple script
showing how this works.

To use it, adjust the script to invoke the right command according to your
system.

Then 'cd' to the user's home directory (one level above 'Maildir') and run the
script with two arguments: the mailbox name (You can use "." for the top-level
folder), and the output mbox filename, for example:

---%<-------------------------------------------------------------------------
cd ~hans
perl dw-maildirtombox.pl . >/tmp/hans-inbox
perl dw-maildirtombox.pl Sent >/tmp/hans-sent
---%<-------------------------------------------------------------------------

---%<-------------------------------------------------------------------------
#!/usr/bin/env perl
# dw-maildirtombox.pl
# dw = Dovecot Wiki :-)
# NOTE! The output file must not contain single quotes (')!
# figure out which program to run
$cmd="reformail -f1";
system("$cmd </dev/null >/dev/null 2>/dev/null") == 0 or $cmd="formail";
system("$cmd </dev/null >/dev/null 2>/dev/null") == 0
or die "cannot find reformail or formail on your \$PATH!\nAborting";
$dir=$ARGV[0];
$outputfile=$ARGV[1];
if (($outputfile eq '') || ($dir eq ''))
{ die "Usage: ./archivemail.pl mailbox outputfile\nAborting"; }
if (!stat("Maildir/$dir/cur") || !stat("Maildir/$dir/new"))
{ die "Maildir/$dir is not a maildir.\nAborting"; }
@files = (<Maildir/$dir/cur/*>,<Maildir/$dir/new/*>);
foreach $file (@files) {
  next unless -f $file; # skip non-regular files
  next unless -s $file; # skip empty files
  next unless -r $file; # skip unreadable files
  $file =~ s/'/'"'"'/;  # escape ' (single quote)
  $run = "cat '$file' | $cmd >>'$outputfile'";
  system($run) == 0 or warn "cannot run \"$run\".";
}
---%<-------------------------------------------------------------------------

Converting from MBX to Maildir
------------------------------

See the uw2dovecot.pl
[http://wiki.dovecot.org/Migration/UW?action=AttachFile&do=view&target=uw2dovecot.pl]
as mentioned on the <Migration.UW.txt> page.

Converting from MBX to mbox
---------------------------

If you are using UW-IMAP and using the <MBX format> [MailboxFormat.mbx.txt],
you will need to convert it to <mbox> [MailboxFormat.mbox.txt] format. The
conversion process isn't pretty, but here is a script that works. You will need
to get and compile the mailutil program from the UW-IMAP web site
[http://www.washington.edu/imap/].

---%<-------------------------------------------------------------------------
#! /bin/sh
# Written by Marc Perkel - public domain
# overhauled by Matthias Andree, 2006
# Usage: mbx-convert <filename>
# This code assumes there a user named "marc" with the primary group "marc".
# Change to any real user on your system.
# Yes - it look bizzare - but it gets the job done
# abort on error
set -e
user=marc
group=marc
homedir=/home/$user
if [ $# -ne 1 ] ; then
  echo >&2 "Usage: $0 <filename>"
  exit 1
fi
# set up automatic cleanup
trap 'rm -f "${homedir}"/in.$$ "${homedir}"/out.$$' 0
# First copy to users home dir and make the user the owner
cp "$1" "${homedir}/in.$$"
chown "$user":"$group" "${homedir}/in.$$"
# Run mailutil to convert as the user other than root
# mailutil requires this
su "$user" -c "mailutil copy in.$$ \#driver.unix/out.$$"
# create new file with same permissions/owner as old
cp -p "$1" "${1}.new"
# cat instead of copy leaves the original owner and permissions alone
if cat "${homedir}/out.$$" >"${1}.new" ; then
  # cat succeeded, rename file into place
  mv "${1}.new" "$1"
else
  # cat failed, remove temp file
  rm -f "${1}.new"
  exit 1
fi
---%<-------------------------------------------------------------------------

Make a copy of some folders and test it first. Once you are satisfied that it
works then:

 * Write a script to convert all your files.
 * Shut down your email system so files can't be modified
 * Copy all your email to a backup location in case you have to revert
 * Run the script
 * Turn on Dovecot and test to verify it is working
 * Important - make sure that you changed your SMTP configuration to write mbox
   and not MBX.
 * Turn on SMTP and verify it is all working

*User comments:*

 * Is this hassle actually necessary? I have run mailutil as root like this
   (mailutil as provided by the PINE 4.61 package for SUSE Linux
   10.0):'mailutil copy /tmp/foo.mbx.orig '#driver.unix//tmp/foo.test'' and did
   not encounter any problems./-- <MatthiasAndree.txt>, 2006-05-18/
 * I did the same (using 'mailutil') but it doesn't maintain UIDs or
   UIDVALIDITY. So I hacked[attachment:mbx2mbox.tgz this] together to do the
   migration./-- <JulianFitzell.txt>, 2008-08-02/
 * Tried to do 'mailutil -v copy /tmp/foo '#driver.unix'/tmp/foo.unix', but
   mailutil argues 'Can't open mailbox /tmp/foo: no such mailbox'. (mailutil as
   from the Debian package uw-mailutils in Debian 5.0 Lenny) strace shows that
   it searches for /tmp/foo/cur, i.e. a Maildir format mailbox. (WTF?) No idea
   yet how to get this working. And I'm really glad when I got rid of MBX. --
   <AxelBeckert.txt>, 2009-06-19
    * As Mark Crispin always says: Don't use UW-IMAP with buggy (Maildir)
      patches, compile your own.
    * Same problem here - just reinstalled uw-imapd, used thunderbird to create
      a "normal" mailfolder and copied the old folder contents - F.Fernandez
    * At least with ubuntu mailutil from uw-mailutils it starts search from
      root *ALWAYS* and if you start with slash it tries to convert from
      maildir format 'mailutil -v copy /tmp/foo '#driver.unix'/tmp/foo.unix' =
      convert maildir formated folder /tmp/foo/cur to mbox and 'mailutil -v
      copy tmp/foo '#driver.unix'/tmp/foo.unix' = convert /tmp/foo file to mbox
      - Manwe, 2010-03-09

(This file was created from the wiki on 2019-06-19 12:42)