User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Firefox/68.0

Steps to reproduce:

Send XMPP messages to a friend.

Actual results:

The messages are only delivered to a single resource.

Expected results:

Keep all IM clients for a user engaged in a conversation by sending outbound messages carbon-copied to all interested resources.

This feature is provided by XEP-0280: Message Carbons. [1]

[1] https://xmpp.org/extensions/xep-0280.html

From looking at the code it seems that there is code to handle message carbons.

Code exists in a few places in xmpp.jsm (see https://searchfox.org/comm-central/source/chat/protocols/xmpp/xmpp.jsm), seems to be controlled by the pref chat.xmpp.messageCarbons, but that defaults to True.

It seems that service discovery (XEP-0030) is used to enable it.

You should be able to check out the protocol log (right click on the account in the account manager) to see if it isn't being enabled for some reason.

As far as I know this is supported, so closing as a dup of bug 964070.

Please reply back if this isn't working for some reason.