TODO
====

* Add an option to resume from a previous failed backup.
* Check storage status before connecting to IMAP server.
* Update messages that have changed in IMAP server.
* Extract message MIME parts, headers and IMAP flags.
* Export messages to standard format (e.g. mbox, Maildir)
* Add support for pushing messages to an IMAP server.
* Add an IMAP server interface.
