Deleting public folders from hybrid environment

Copper Contributor



I have an hybrid Exchange environment everything is running ok, but now I am starting to take on the task of eliminating the public folders which are in the on-prem Exchange server (2010) and recreate them in O365 or delete them.


So I have a mail enabled public folder in my on-prem environment.  I went ahead and from the on-prem Exchange console, I changed the folder to "Mail Disabled".  I then ran Azure sync.


The problem is that I cannot create a shared mailbox on O365 with the same SMTP address because I get the following error:


The proxy address "" is already being used by the proxy addresses or LegacyExchangeDN of "PublicMailboxName". Please choose another proxy address.( The "PublicFolder" with display name "PublicMailboxName" is already setup and using the same address.)


When I do the Azure sync I don't even see where it is replicating the fact that I removed this SMTP locally.  Any suggestions on what I can do to make this happen??

3 Replies

So there are two things in play here. First, newer versions of AAD Connect have the "sync public folders" feature, but that only pertains to mail flow (enabling said addresses to receive messages when DBEB is enabled). In such scenarios, you can simply remove the address on-premises, wait for sync to happen. Details are here:


Another scenario is when you have configured "co-existence" for PFs and are running a script to "manually" synchronize them. In this scenario, it's a matter or rerunning the script. Details are here:


@Vasil Michev So we have no public folders in Exchange Online at all, nor do they show up in the UI.  Our public folders only reside on-prem.  So I assume we aren't doing the script in the second option.


I checked our Azure Sync, and the "Exchange Mail Public Folders" option is unchecked.  Are you basically saying now that I have mail disabled on that public folder, I should enable that option in Azure Sync and do a full sync?

None of the methods I mentioned will actually result in creating PFs in Exchange Online. What they do is create a "representation" of the PF object, so that ExO can handle mail flow for it. This usually takes the form of a mail user, but if you've played with things manually can be other recipient types as well.


There's no need to enable said option on your AAD Connect install, if it's unchecked it simply means you are not using that method. Check with your peers whether the other method (running a PS script/scheduled task) is used. And run the following in ExO to give you an idea what kind of object you have for said address: