When launching the App, you are taken to the Composing Screen. Here you create new messages.
The To: field is used to enter the person you are sending a message to; its the mailbox name. Think of the To: field as a secret name, not a commonly guessed name. For example, if you want to send a message to Alice, why not use alice-salsashoes, or maybe alice-89t22c. You can use email address sounding names, such as email@example.com. Most kinds of characters you can type are accepted, so long as its not too long.
We assume the recipient already knows the message mailbox. You might already have been talking to them over the phone, Skype messaging, or iMessage, for example.
Pressing Next will take you to the field where you can type in the message body. So long as the message is not too long, the message will be sent when you press the Send button. This button originally starts as saying Next. When both the To: field and body text have been filled out, the button switches purpose from a Next button to a Send button.
An optional setting is to set the message self-destruct time. Whilst in the message body editing mode, press Dismiss, to dismiss the keyboard to reveal the slider where you can select the self-destruct time. This can be as short as 30 seconds or as long as 20 minutes.
The idea behind this feature is that you as sender will have an idea how long it takes to understand the message being sent. If you are sending some data which is complex, like a postal code (zip code), then that would need time to write down at the recipient end. If you are sending a quick easy to comprehend message, for example a time to meet up, then that takes less time to comprehend.
We want the message to automatically delete once it has been read by the recipient. If they do not try to read the message for some days, the message lives until it is read. Once read, the self-destruct timer starts. The message is silently deleted after the specified time. This means the user is not warned about it in advance. The user can chose to delete the message straight away.
When the phone is shaken, the message being written or read is automatically deleted. When the clock is changed significantly on the phone to some other time, or if the screen snapshot is taken, then the message is deleted.
It takes only a few seconds to send a message. This requires a data or cellular connection. Not much data is used.
The receiver of the message is not notified when a message comes in. They need to retrieve a message using the mailbox name. The mailbox name is sensitive to character case, spaces, and any other character marks. So if the mailbox name is quite complex to type in there is a chance of user error. If the mailbox name is too easy to guess, then someone else might read the message. It is a balance that needs to be struck.
The mailbox name is specified once the user goes into the bottom tab called Receive Message. It is called From: in the user interface.
It is recommended that the message is manually deleted as soon as possible. But if you forget to do this, it will be automatically deleted.
If two messages are sent to the same mailbox before the mailbox has been read, then the messages are joined (concatenated) together so long as the overall length of the message is not too long.
In practice the best way is to have two mailboxes, one for each person in the conversation, so one person only reads from a mailbox, and one person only writes to a mailbox.