Messages are temporarily stored on service node network for a time period of 14 days, this is known as the message's 'time to live' (TTL).
Messages are stored for this time period to ensure messages are successfully delivered even if the receiver is offline when the message is sent.
All messages and data are encrypted, and message origins are obfuscated using onion routing network, so service nodes don't have access to any identifying information or sensitive data.
Once the TTL of a message has expired (14 days), it is deleted from the network and the only copies are stored locally on devices of the message sender and receiver.