Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
Dear Kay,
Good day! Thank you for posting to Microsoft Community. We are happy to help you.
Based on your description, it seems that you want to set up the automatic reply for users via PowerShell, we kindly suggest you refer to Set-MailboxAutoReplyConfiguration (ExchangePowerShell) | Microsoft Docs to get more details.
If you want to set up the AutoReply for all users in your organization, we kindly suggest you post this question on our dedicated PowerShell communities: PowerShell community support resources - PowerShell | Microsoft Docs. Experts there might available to provide you further assistance to let you know which cmdlet can make it be org-wide.
Sincerely,
Tommy | Microsoft Community Moderator