Short Messages is the way to interact with legacy SIP IM clients that do not support session based Chat Sessions using MSRP protocol.
Short Messages are stand-alone entities that operates in a fire and forget fashion. There is no guarantee for delivery or alerting of the final recipient. Short Messages end-up on all SIP devices registered for the remote SIP Account, including hardware phones that accept such messages but do not display them, the recipient has no control where to receive them.
Short Messages have no end-to-end delivery report and cannot be encrypted the way Chat Sessions are. For guaranteed message delivery and encryption you must use Chat Sessions.
A Short Message cannot exceed 1300 characters on IP networks and 160 on PSTN mobile networks.
You can send a Short Message by right-clicking on a Contact and chose Send SMS.
Previous exchanged messages can be reviewed in the menu Window->Chat History.