Migrate mailboxes with their calendars and contacts between servers, in bulk, from a web dashboard.

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Overview

mccb (Mail Contact Calendrier Bridge) moves mail, calendars, contacts and tasks from a source to a target, one mailbox at a time, and runs as many mailboxes in parallel as the machine and the servers allow. It started as a PST importer and now reads and writes the usual protocols. Free, for good: MIT licence, no paid edition.

Quick start

mkdir mccb && cd mccb
curl -fsSLO https://raw.githubusercontent.com/selfhostr/mccb/main/docker-compose.yml
docker compose up -d
docker compose logs web | grep -A2 "Admin password"

Open http://<host>:22362 and sign in with the printed password (shown once). Port 22362 speaks plain HTTP: put it behind a reverse proxy with HTTPS. Back up ./data, including secret.key: without it the stored mailbox passwords cannot be decrypted. More in install.

Features

• Many sources. PST and OST, mbox, Maildir, .eml, .msg, .ics, .vcf, IMAP, CalDAV, CardDAV, Exchange, Microsoft 365, JMAP, Google: connectors.
• Built for batches. Add mailboxes one by one or by CSV, run them all, read one report per mailbox.
• Built for big sources. Resumable uploads, a drop folder, server-side fetch, preview and dry run.
• Safe to interrupt. Pause, stop, crash or restart: a resume checks the target and never duplicates an item.
• Plan and control. Folder mapping, date and size filters, allowed hours, bandwidth limit, final resync: planning.
• Command line. mccb uploads with resume, plans, runs and watches with API tokens: cli.
• Notifications. ntfy, webhook or e-mail when a migration finishes: notifications.

Architecture

One image, two services: web (FastAPI and a static UI, port 22362) and worker (job queue). Every job and every PST analysis runs in its own subprocess, so a crash of the native PST library cannot take the worker down. State is SQLite and files in ./data. See how it works.

Limits

• Exchange, Microsoft 365 and Google were tested against simulated servers only, never the real services. Try one mailbox first.
• JMAP calendars are not carried: use CalDAV with the same provider.
• One administrator and SQLite on a local disk: one host, no high availability.
• A source is read in one pass, not synchronised: later changes at the source are not carried over.
• Results depend on the target IMAP and DAV server. More in known limitations.

Contributing

Issues and pull requests are welcome: CONTRIBUTING.md. Security issues: SECURITY.md.

License

MIT, see LICENSE. Provided "as is", without warranty of any kind.

Support

mccb is free and has no company behind it. If it saves you time: sponsor us on GitHub.