Recently I needed to do some maintenance to 1 of the members in our 3 node Exchange 2013 DAG. I put the server in maintenance mode using the following commands.

Set-ServerComponentState servername Component HubTransport State Draining Requester Maintenance
Suspend-ClusterNode Name servername
Set-MailboxServer servername DatabaseCopyActivationDisabledAndMoveNow $true
Get-MailboxServer servername | Select DatabaseCopyAutoActivationPolicy
Set-MailboxServer servername DatabaseCopyAutoActivationPolicy Blocked
Set-ServerComponentState servername Component ServerWideOffline State InActive Requester Maintenance

Once all of the commands had run I confirmed that the server was in maintenance mode before I began updating that server. Once I began updating the server, I got a call from a user that they can't send email. They received an NDR that said their email could not be delivered. I had the user try and resend the email and it went through fine. My question is, how do I prevent from happening in the future? I thought once the server was in maintenance mode it could not be contacted by clients. Should I also add I line to my script that also stops the transport service to prevent any connections? Any help would be greatly appreciated.

Thanks

I went back over some of my notes on this and found that the user didn't get an NDR. The received the following error in their Outlook client for Mac.



This shows me that he must have gotten this error while I was moving the data store that his email box is associated to. 

• Marked as answer by TRDx2 13 hours 52 minutes ago