User has cloud and on premises mailbox. How to keep the cloud one and delete the on premise one?

[Robert K]

User was created cloud-only (with a enterprise E3 licence) a long time ago and therefor has a cloud mailbox. Months later, Azure AD Sync and Hybrid Mode have been set up. The user also has a mailbox in the local on premises Exchange.  Login name and email address are the same: userx@contoso.com. The account should now be migrated to the cloud. How can I ensure that the cloud mailbox remains intact during the migration and that the on premises mailbox is deleted?

[#2]

Hi @Robert K ,

Has this user's account been synced with Azure AD Connect, or are there two different accounts (one cloud/one on-prem) that need to be merged?  I know there are several ways to set up conflict resolution and attribute matching in an AADC hybrid scenario, so the steps to accomplish this would differ significantly depending upon the state of the account(s).

[#3]

@Adrienne Andrews "two different accounts (one cloud/one on-prem) that need to be merged" is correct.

[#4]

you can take the PST of the local mailbox and then just disable local mailbox and enable remote mailbox.