For questions related to the Briar Android app, see [the respective FAQ](https://code.briarproject.org/briar/briar/-/wikis/FAQ).
# Why does each user needs their own mailbox?
_to be answered_
# When I introduce two contacts to each other, do they need to come online at the same time to start using their mailboxes?
Yes, they need to be online at the same time at least once before they can communicate via mailboxes.
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Yes, they need to be online at the same time at least once before they can communicate via mailboxes.
The reason for this is that despite all transport properties (Tor, LAN, Bluetooth) being exchanged during introductions, mailbox addresses aren't usual transport properties and are therefore unknown to contacts before being online at the same time for the first time.