Openfire supports XEP-0280: Message Carbons, which keeps all IM clients for a user engaged in a conversation. Outbound messages are carbon-copied to all interested resources.
This feature is enabled in Openfire by default. If a client wants to use the Carbons protocol, it needs to enable it by sending an IQ stanza containing a child element <enable/> qualified by the namespace “urn:xmpp:carbons:2” as shown in the following example: