Migrate on premises Exchange Server 2016 to Office 365 public folders failed

We're migrating from on premises Exchange Server 2016 to Office 365.

Users accounts migrated fine and are using the system without problem.

Public folders failed, and disappeared from on premises and didn't show on Office 365.

After many hours troubleshooting with Microsoft, I decided to delete all Public Folders and manually recreate them in Office 365.

Since they disappeared, ECP was of no help so I deleted them using ADSI Edit. After everything sync'ed, I verified that they are gone on premises.

Now when I try to create them in Office 365, it says that the email address exists. It doesn't in on premises, but I can see them in Outlook -> People online.

I can't send or receive mail using those addresses and I need to delete them so I can recreate them correctly.

Make sure there aren't any existing public folders or public folder mailboxes in Exchange Online. Get-Mailbox -PublicFolder Then check which mailbox using this email address by get-mailbox| where {$_.EmailAddresses -match "user name"} | ft Name, RecipientType, EmailAddresses and change it.

Or you could check the sync status in AAD connect, find the source object (on-premise) and delete it in Exchange 2016.

Troubleshoot an object that is not synchronizing with Azure Active Directory https://docs.microsoft.com/en-us/azure/active-directory/hybrid/tshoot-connect-object-not-syncing>