Vandelay is a one-shot account migration utility for JMAP, similar to
imapsync but covering every JMAP data type: mail, contacts, calendars,
identities, sieve scripts and file storage. It is developed by Stalwart
Labs, the authors of mail/stalwart.

An account is first imported into a self-contained local SQLite archive
from JMAP, IMAP, CalDAV, CardDAV, WebDAV, ManageSieve, Maildir++, a
Google Takeout export, Microsoft Exchange Server (EWS) or Exchange
Online (Microsoft Graph). The archive is then exported into a target
JMAP server. Both steps can be interrupted and re-run and pick up where
they left off.

Because one archive fully describes one account, Vandelay also serves
as a per-account backup tool: periodic imports refresh the snapshot and
an export restores it.
