History
Keep prior correspondence
Confirm whether the organization needs the existing mailbox contents retained and who is authorized to review them.
Everyday IT · Microsoft 365 & Email
Preserve the mailbox without preserving the employee's sign-in.
Departures become messy when mailbox access, account access, retention, delegation, and licensing are treated as the same thing.Decide what the business needs to keep, then choose the mailbox and permission model that supports it.
Start with the business requirement
Before changing anything, determine whether someone needs historical mail, future incoming mail, send-as capability, or only a temporary review period.
Future mail
Decide what new messages should do
New mail may need to continue arriving, be delegated to a successor, or be handled through another approved business process.
Identity
Do not hand out the former user's password
Mailbox access should normally be provided through approved delegation rather than preserving or sharing the departed employee's interactive sign-in.
A safer operational pattern
The exact licensing and retention rules can vary by tenant and Microsoft policy, so verify the current environment before making irreversible changes.
1
Confirm the mailbox still exists and is healthy
Check the object, mailbox state, and expected content before changing account or licensing settings.
2
Choose the intended mailbox model
If the mailbox is becoming a team-held historical resource, a shared-mailbox design may be appropriate. Do not assume conversion is always the answer without checking size, archive, retention, hold, and licensing requirements.
3
Grant named users only what they need
Use mailbox permissions instead of generic credentials. Reading and sending are separate capabilities.
4
Verify from the successor's Outlook or web client
Confirm the delegated mailbox appears, historical mail is present, and sending behavior matches the request before removing any remaining recovery path.
When to stop and escalate
Retention
Legal hold, archive, or compliance requirements exist
Do not change mailbox type or licensing until retention obligations are understood.
Recovery
Older mail is already missing
If content appears absent, stop treating the task as simple delegation. Recovery, backup, retention, or restore procedures may be required.
Unclear
The owner cannot say what should be preserved
Get a business decision before changing the mailbox. Technical convenience should not decide retention policy.
Keep the business data. Remove the unnecessary identity risk.