There are TWO mailboxes for the same user, one on-premise and one in Exchange Online

Issue

There are TWO mailboxes for the same user, one on-premise and one in Exchange Online

Solutions

1. In most cases, the issue is caused when the newly created user has not been given sufficient time to sync the Exchange attribute and the Office 365 license is applied too quickly. When creating a new user with an on-prem mailbox allow 30 minutes for the sync to complete, you can also force the sync using the following command or GUI from DC01
   • Open Windows PowerShell and type:
     • Start-ADSyncCycle -policytype Delta
   • Option 2 – Open Azure AD Sync Service on DC01 (Start>Azure ADConnect)
     • Right click ‘Delta Sync’ and select ‘run’and select ‘Delta Synchronization’ and ‘OK’
   • Make sure the Azure AD sync is up to date, not an issue for CloudM right now but it is recommended to keep Azure AD connect updated. The latest version can be downloaded from Microsoft Website.