The Samba-Bugzilla – Bug 4538
smbclient should be able to send messages to an entire workgroup/domain
Last modified: 2007-06-19 10:31:15 UTC
That bug was initially reported (long time ago!) against linpopup in Debian.
It turns out that this feature request indeed pertains to smbclient and can be summarized as "should be able to broadcast messages to a workgroup/domain"