Backup and restore IMAP mail account with (open source) Linux tools

**Which Linux tools help to backup and restore a IMAP mail account including all mail and subfolders?** I expect disconnects for large IMAP accounts because of 1. ressource limitiations on the server 2. risk of an interruption increases with the duration. The software should be able to reconnect and continue the job after any interruption. For repeating backups it might be very handy to use incremental backups and to run the backup script in a cron job.