When the External Storage Mode setting is set to AirSync, the Account Mailbox storage is synchronized with the external mailbox storage system using the AirSync protocol:
- The mailbox tree is synchronized every time a mailbox listing operation is applied to the Account
- Mailbox creation, renaming, deletion operations are applied to the external mailbox storage first, and then the mailbox trees are synchronized.
- Each Mailbox is synchronized when it is being opened and then periodically while the Mailbox is kept open.
- When a message or other item is being moved from one Mailbox to a different Mailbox, this operation is applied to the external mailbox storage, and then both Mailboxes are synchronized.