Decision rule
If multiple people need to work out of one inbox, track ownership, and preserve continuity, use a shared mailbox.
If you only need to distribute copies to individuals, use a distribution list.
Messaging semantics (what each object actually does)
Distribution list (DL)
A DL is a delivery mechanism. When a message arrives, Exchange expands the group membership and delivers a copy to each recipient. There is no shared queue and no shared message state. Each user manages their own copy.
Shared mailbox
A shared mailbox is a mailbox. Messages arrive in one location, and access is controlled by delegation. This supports triage, continuity, shared categorization, and operational handover if configured correctly.
Comparison matrix (operational reality)
| Capability | Distribution list | Shared mailbox |
|---|---|---|
| Shared queue | No. Messages are copied to individuals. | Yes. Messages land in one inbox. |
| Ownership / triage | Manual. Requires process outside Exchange. | Built-in patterns (categories, flags, shared folders). |
| Continuity | Low. Knowledge stays with individuals. | High. History remains in mailbox. |
| Sending identity | Generally not used as a sending identity. | Common. Requires Send As / Send on Behalf governance. |
| Auditability | Hard. Multiple independent copies. | Better. Single mailbox history if sent item copy is configured. |
Governance considerations
In production environments, “mailbox design” becomes a governance problem:
- Who owns membership/delegation changes?
- Who is authorized to send as the mailbox?
- How are sent items retained for shared visibility?
- What is the external mail policy (allowed or blocked)?
Implementation verification checklist
DL verification
- Confirm membership source (static members vs dynamic group).
- Confirm whether external senders are allowed.
- Confirm moderation requirements if needed.
Shared mailbox verification
- Confirm Full Access delegation.
- Confirm Send As or Send on Behalf (explicitly choose one model).
- Enable sent items copy settings if operational continuity requires it.
# Example sent items copy settings for shared mailbox continuity Set-Mailbox -Identity shared@domain.com ` -MessageCopyForSentAsEnabled $true ` -MessageCopyForSendOnBehalfEnabled $true