Store and forward.
Why your message arrives even when their phone is dead. Instead of requiring both people online at once, the network holds the sealed message and forwards it the moment the recipient reappears — the same model email has used for fifty years.
Store and forward is a messaging pattern where an intermediary accepts a message, stores it while the destination is unreachable, and forwards it on reconnection. CarrierPony's relay implements it for end-to-end encrypted envelopes.
What it is
Your phone uploads the sealed envelope once, regardless of whether your contact is reachable. The relay queues it, pings the recipient's phone through push notifications, and delivers on the next connection — then deletes its copy.
Why it matters
Asynchrony is what makes messaging humane: people answer when they can. The trick is doing it without a readable mailbox on someone else's server, which is exactly what sealing envelopes end to end before storage achieves.
Related terms
Common questions.
How long are undelivered messages kept?
Until delivery or a bounded expiry, whichever comes first. The relay is a conveyor belt, not an archive.
Does the sender know when delivery happened?
Your app reflects the envelope's progress. What the relay itself learns stays at the routing level — it never learns what was inside.
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Free private messaging and file transfer for iPhone. No accounts, no tracking, no phone numbers.