Migrating from any IMAP/POP3 server to Dovecot

You can also do the following on the command-line without configuration files:

# doveadm -Dv  \
  -o imapc_host=<SOURCE_HOST> \
  -o imapc_user=<SOURCE_USERNAME> \
  -o imapc_password=<SOURCE_PASSWORD> \
  -o imapc_features=rfc822.size \
  -o imapc_ssl=starttls \
  -o mail_fsync=never \
   backup -R -u <DESTINATION_MAILBOX> imapc:

I had great problems, because my source IMAP only supports STARTTLS on port 143. -o imapc_ssl=starttls was a life-saver in my case.

You can make a sync after the initial backup with:

# doveadm -Dv \
  -o imapc_host=<SOURCE_HOST> \
  -o imapc_user=<SOURCE_USERNAME> \
  -o imapc_password=<SOURCE_PASSWORD> \
  -o imapc_features=rfc822.size \
  -o imapc_ssl=starttls \
  -o mail_fsync=never \
  sync -1 -R -u <DESTINATION_MAILBOX> imapc:

Of course, this is quite insecure if you have more users on the box that can see your commands (and passwords) with who or by looking into your .bash_history file, so beware.

If the two mail servers are running without problems with the IMAP protocol I would use imapsync to do the job. Both Courier and Dovecot are supported by imapsync.

It's really straightforward to use and support many features, like regexp mappings for different folder synchronisation.

The software is FOSS and can be found here: http://imapsync.lamiral.info

If you need the UID sync you can add the option --useuid in the imapsync. I'm not sure if you're talking about this kind of UID. But this is the option that you should be looking for:

--useuid : Use uid instead of header as a criterium to recognize messages. Option --usecache is then implied unless --nousecache is used.

You should migrate your mail using the dsync utility from Dovecot. This will preserve the UIDs and even POP3 UIDLs if necessary.

Run dsync using the backup -R option, to 'reverse backup' from the remote IMAP server to the local Dovecot server. You need to have a special configuration file created, something like this:

imapc_host = imap.company.com
imapc_user = %[email protected]
imapc_password =  mypassword
imapc_features = rfc822.size fetch-headers
imapc_port = 143
pop3c_host = pop3host.company.com
pop3c_user = %[email protected]
pop3c_password = mypassword
pop3c_port = 110
namespace pop3c {
   prefix = POP3-MIGRATION-NS/
   location = pop3c:~/pop3c
   list = no
   hidden = yes
}

!include /etc/dovecot/dovecot.conf

plugin {
  pop3_migration_mailbox = POP3-MIGRATION-NS/INBOX
  pop3_migration_skip_size_check = yes
  pop3_migration_ignore_missing_uidls=yes
}
mail_prefetch_count = 20
mail_shared_explicit_inbox = no
protocol doveadm {
  mail_plugins = $mail_plugins pop3_migration
}

Note this is for a single user; you may want to have different options if you use a master user/password, or if you require SSL for the connections.

Then call it with something like: dsync -D -v -u username -c configfile.cfg

The username replaces the %u in the config.cfg file. The -D -v is verbose debug mode.