Imapsync

Imapsync is a command line tool that can transfer mail between mailboxes on different servers using IMAP. The software can be run from Linux or Windows – please see http://imapsync.lamiral.info for more information.

If you have a lot of emails to migrate, consider running Imapsync some days or even weeks prior to actually switching to using Zimbra live. After the initial full sync has completed, you can continue to perform synchronisations leading up to the go live date and the sync will be much faster as there will be less data to transfer.

The following is an example command-line shell call of imapsync tailored for Zimbra:

imapsync /
–host1 {customers server} –user1 {username} –password1 {password} /
–authmech1 LOGIN –ssl1 –sep1 –prefix1 INBOX. /
–host2 zimbra.protectedservice.net –user2 {user@customer.com} –password2 {password} /
–prefix2 Transferred/ –authmech2 LOGIN –ssl2 –sep2 /
–syncinternaldates –buffersize 8192000 –nosyncacls –useheader ‘Message-ID’ –skipsize

The above command transfers the mail into a folder in Zimbra called “Transferred”. We recommend doing this rather than delivering directly into the Inbox since you can more easily check the content and it’s easy to move the contents of Transferred once the migration has finished.

If the source server does not support SSL or requires a different authentication method, you will need to adjust the switches accordingly. https://imapsync.lamiral.info/#doc for all configuration options.

Zimbra’s wiki contains a guide on how to use imapsync with Zimbra.