Inactive Mailbox Deep Dive

Migrating to Exchange Online present it’s own set of challenges. Understanding the behavior of the mailbox governance and compliance, it’s an entirely different subject.

Many of my customers have one thing in common, they get overwhelmed with Microsoft docs. While I enjoy reading, not everyone has the bandwidth or time to delve into the many articles or documentation online. I mean, surfing the web never comes back empty handed but, doesn’t always have the right answers in one place.

In this article, I hope to alleviate some of the frustration we wall face when trying to explain to our customers the impact to Exchange Online mailboxes when the mailboxes is either deleted, disabled, or inactive.

Understanding the different kinds of events that can impact a user mailbox

What happens to the mailbox if…ImpactState
The Exchange Online license is removed?When you remove the license, all that user’s data is held for 30 days.Soft-Deleted
The user is removed out of scope in AAD Connect?The mailbox is deleted.  The user’s data is held for 30 days.Soft-Deleted
The user is disabled in AD?The mailbox will remain in Exchange Online.Active
The user is disabled in Azure AD?The mailbox will remain in Exchange Online.Active
The user deleted in Azure AD?The mailbox is deleted.  The user’s data is held for 30 days.Soft-Deleted
The user is deleted in AD?The mailbox is deleted.  The user’s data is held for 30 days.Soft-Deleted

What is the difference between deleting and disabling a mailbox?

ActionImpactRecovery PeriodState
Deleting a MailboxExchange attributes are removed from the corresponding Active Directory user account, but the user account is retained.30 days by defaultSoft Deleted
Disabling a MailboxThe user account that’s associated with the mailbox remains, but it’s no longer associated with a mailbox.The mailbox isn’t deleted and can be reconnected to its user at a later date.Disconnected

Recovery Period before 30 days

ActionImpactStateLocationRestore
Deleting a MailboxExchange attributes are removed from the corresponding Active Directory user account, but the user account is retained.Soft DeletedThe mailbox will be moved to the Exchange recycle bin.The method for restoring a mailbox depends on whether the mailbox was deleted by deleting the user account or removing the Exchange Online license.
Disabling a MailboxThe user account that’s associated with the mailbox remains, but it’s no longer associated with a mailbox.DisconnectedThe mailbox is in Exchange Online database.Connect-Mailbox

Recovery Period after 30 days

ActionImpactStateLocationRestore
Deleting a MailboxExchange attributes are removed from the corresponding Active Directory user account, but the user account is retained.Hard DeletedThe mailbox will be purged from Exchange. Online.  The data will not be recoverable.   The option of a Litigation Hold or In-Place Hold to a specific Exchange Online mailbox; this option overrides any existing Deleted mailbox retention policy.  If Litigation Hold or In-Place Hold are set, the mailbox will be set to an inactive state.New-MailboxRestoreRequest
Disabling a MailboxThe user account that’s associated with the mailbox remains, but it’s no longer associated with a mailbox.DisconnectedThe mailbox is active in Exchange Online database.Connect-Mailbox

Exchange Online Data Deletion in Microsoft 365

Exchange Online Data Deletion TypesService Retention PolicyImpactLimitations
Soft DeletedDeleted mailbox retention policyIn Exchange Online (Office 365) mailboxes for a period of 30 days by default.     Exchange Online administrator cannot extend the specified time.
Hard DeletedDeleted mailbox retention policyDate purgeAll mailbox content such as emails, contacts and files are permanently deleted.

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