mailbox.connected
mailbox.connected fires when a customer finishes authorizing a Gmail or Outlook mailbox, carrying your ref and metadata to match it to a user.
A customer finished authorizing a Gmail or Outlook mailbox.
Payload
Every field, with an example body, is in the mailbox.connected reference, generated from the API contract.
Handling it
This — not the browser landing back on return_to — is the signal that the mailbox is live. The redirect happens whether or not the grant completed, and a customer who closes the tab never triggers it at all.
Match on ref — whatever you put on the connect link or passed to mailboxes.connect — to attach the mailbox to the right user in your database. Anything more you need at this point belongs in metadata, not JSON-encoded into ref.
On a reconnect, ref and metadata are what the mailbox holds now: what the new link carried, or what was there already where it carried none.
Mailboxes
The connect flow end to end, including your own OAuth app.