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+Mialbox screens do not show any messages, therefore the user cannot know if their messages were correctly uploaded or not.  For the user, that is all black box. 
+
+For testing purposes, though, it should be possible to verify this by looking into a logfile of some kind.
+It would be good if this logfile also shows the acknowledgements that the Mailbox sends to Briar.  
+
+In Briar, the messages uploaded to Mailbox (either own or the contact's) will show only as sent messages.  For the user, this will be identical to messages being exported via removable media, ie they will have 'one tick'.
+
+This phase is also present when messages are sent directly to the contact who is online, but it is too brief to be seen by naked eye.  In this case the contact's Briar app sends the ack immediately, and at this point the sent messages on the senders Briar app show 'two ticks'.
+
+When the contact comes online, the Mailbox will notice and forward them the messages it has uploaded earlier.  At this point, there is still no change in the message status on the sender's screen, it still has only one tick.  So the sender will not know when the message is forwarded from Mailbox to the intended recipient, nor whether it was done via own mailbox or the recipient's.
+
+Once the recipient's Briar app received a message from their own or from the contact's mailbox, their Briar app will send the ack 
+- directly to contact if their contact is online, and at this point the sender will see their sent message get the second 'tick'
+- via own or contact's mailbox.
+
+Scenarios: 
+
+| sender | online | has mailbox | maibox online | recipient | online | has mailbox | maibox online |
+| ------ | ------ | ------ | ------ | ------ | ------ |------ | ------ |
+| ------ | yes | yes | yes | ---- | no | no | na |
+| ------ | ------ | ------ | ------ | ------ | ------ |------ | ------ |
+| ------ | ------ | ------ | ------ | ------ | ------ |------ | ------ |