IMAP synchronization, copy and migration tool The command imapsync is a tool allowing incremental and recursive imap transfer from one mailbox to another. Sometimes mailboxes needs to transfer 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. It can be stoped the transfer at any time and restarted later, imapsync is adapted to a bad connection. It can decided 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. It can be also just synchronized 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.