We have Exchange Hybrid setup. In exchange admin center we would like to understand the different between creating “User mailbox” vs “Office 365 mailbox”.
The problem is when we create a new in active directory and it gets sync. The mail box is creatd with MailboxType = User and RecipientType = UserMailbox. However when we create it from EAC console as Office 365 mailbox the Mailbox Type is set to Office 365 and RecipientType to MailUser. We would like to understand what different it would make and if there is a possibility of creating Office 365 mailbox from AD Sync.
User mailbox means creating mailbox in your local DB, O365 mailbox means creating mailbox in O365. If you login to O365 you will be able to see mailboxes there, which are displayed here as mail users. Recipient type is "mail user" so that your on premises exchange knows that there is a corresponding mailbox for this object in O365.
like they mentioned, the mailuser object is created so that on-prem knows to put that object in the GAL for on-prem users and knows that it can accept mail for that address and forward it along to EOP to deliver it to O365.