You want your app to have its own copy of a user's email: to search it fast, run analytics over it, or feed it to a model without hitting the provider on every query. The naive version is a one-time pull that's stale the moment it finishes, because new mail keeps arriving and old mail gets read, moved, and deleted. A real sync is two jobs working together: backfill the history once, then track changes forever after. This post builds that out with the Email API and shows the CLI shortcuts for testing each piece.
It's a worked use case rather than an endpoint tour, pulling together list messages, cursor pagination, and the message webhooks from two angles: the HTTP API your backend runs and the nylas CLI for the terminal. I work on the CLI, so the commands below are the ones I reach for when I'm checking what a sync will actually see.
The two phases of a mailbox sync
A durable sync splits into a backfill and a tail. The backfill is a one-time walk through every message already in the mailbox, page by page, writing each into your database. The tail is the ongoing part: webhooks tell you about each new message, each change, and each deletion as it happens, so your copy keeps pace with the real mailbox instead of drifting from it.
