When an Instant Message request is delivered to a CommuniGate Pro Account, it is processed as any other Signal Request - Signal Automated Rules are applied, the request is forked to all active XIMSS and XMPP sessions, and, optionally, to registered SIP devices.
Incoming and outgoing IMs are stored in the Account File Storage.
If an IM cannot be delivered because there is no session or device to relay it to, the message is appended to a special file in the Account File Storage. When the Account user launches an XMPP or XIMSS client application, all stored IMs from that file are delivered to the user via that client application, and the file is removed.
Incoming IMs can be rejected without processing if the IM sender is not a confirmed Buddy in the Account Roster. See the Preferences section below.