Why does it take a longer time sometimes until a message is sent to or received by the recipient?

Since twinme messages are exchanged in peer-to-peer, directly from device to device, without a store and forward server in the middle, both your device and your contact’s need to be online simultaneously for messages to be actually transferred.

With other server-based chat services, your message may be immediately sent to the server, but not necessarily to the actual recipient if the latter is not online.

With twinme, when a message is said to have been sent, it means it has been actually received (but not necessarily read) by the recipient.

Why does it take a longer time sometimes until a message is sent to or received by the recipient?

Since twinme messages are exchanged in peer-to-peer, directly from device to device, without a store and forward server in the middle, both your device and your contact’s need to be online simultaneously for messages to be actually transferred.

With other server-based chat services, your message may be immediately sent to the server, but not necessarily to the actual recipient if the latter is not online.

With twinme, when a message is said to have been sent, it means it has been actually received (but not necessarily read) by the recipient.