UbuntuUpdates.org

IMAP synchronization, copy and migration tool
The command imapsync is a tool allowing incremental and recursive imap
transfer from one mailbox to another.

We sometimes need to transfer mailboxes from one imap server to another.
This is called migration.

imapsync is the adequate tool because it reduces the amount of data
transferred by not transferring a given message if it is already on both
sides. Same headers, same message size and the transfer is done only
once. All flags are preserved, unread will stay unread, read will stay
read, deleted will stay deleted. You can stop the transfer at any time
and restart it later, imapsync is adapted to a bad connection.

You can decide to delete the messages from the source mailbox after a
successful transfer (it is a good feature when migrating). In that
case, use the --delete option, and run imapsync again with the --expunge
option.

You can also just synchronize a mailbox A from another mailbox B in case
you just want to keep a "live" copy of B in A (backup).

Similar packages: offlineimap, imapcopy.