Jmap-backup: Back up Fastmail mailboxes to standard EML format files

The jmap-backup is a Python program aimed at backing up messages from Fastmail's JMAP mailbox, based on the work of Nathan Grigg. To use the program, users need a Fastmail API key, which can be obtained from Fastmail settings, and either Docker or Python 3 with the `requests` module installed. For local setup, users should download the latest release or clone the repository, copy the `jmap-backup.py` script to a directory in their `$PATH`, and create a JSON configuration file that includes at least the `dest_dir` and `token` keys. The backup can be initiated with a specific command. For Docker users, the process involves cloning the repository, creating necessary directories, setting up a configuration file, building the Docker image, and running the container. Additional configuration options are available in the config file, allowing users to customize parameters like `delay_hours` and `not_before`. The program includes a verification feature to ensure that all messages in the mailbox are backed up correctly. It is designed for efficiency and can be scheduled for regular backups, such as through cron jobs.

- jmap-backup is designed for backing up Fastmail JMAP mailboxes.

- Users need a Fastmail API key and either Docker or Python 3.

- The program can be run locally or within a Docker container.

- Configuration options allow for customization of backup parameters.

- The program includes a verification feature to ensure message integrity.