You could have a wallboard with a message, but that would only work if they are looking at it.
Second, could consider an SMS message campaign that could contain all their cell numbers and use a template to setup the message that will be going out to them.
Lastly, you could create a public chat group and send a message to that group. A group voicemail will do the same. With the new voicemail transcription coming out next week, they could read the voicemail in their email.
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Robert Wakefield-Carl
TTEC Digital, LLC fka Avtex Solutions, LLC
Contact Center Innovation Architect
https://www.ttecDigital.comhttps://RobertWC.Blogspot.com------------------------------