I use Cisco Jabber registered on CUCM.
Is there any option to send to all users some message in pop up?
If I understood your requirements correctly, you can send a broadcast message from your Jabber client,
1. Select all the contacts from your Jabber
2. right click and select send the broadcast message
3. new message window open and type your message and then click send
the recipient will receive messages in the same way as one to one message.
Please rate useful post and mark answered if relevant.
Then no, you cannot, you'll need to find some other way.
Find answers to your questions by entering keywords or phrases in the Search bar above. New here? Use these resources to familiarize yourself with the community: