When using IMs, we might see some messages that is not sent by any contact but the IM it self. These messages will appear in conversations like regular messages, but usually in different font and color. e.g.:

Lark:

Whatsapp:

Wechat:

Wecom:

Thus we need a new message type: System. It's almost the same with text messages. The talker should be the contact and the listener should be the user self.