A colleague replies from the sales mailbox, but the rest of the team cannot find the response in its Sent Items folder. That does not, by itself, prove the message failed to leave. The sent-copy location and message delivery are separate questions.
For a shared accounts or customer-service mailbox, the practical requirement is clear: authorised colleagues should be able to see the correspondence they need without relying on one employee’s personal mailbox.
Original illustration distinguishing an outgoing message from its personal and shared sent copies, not an Outlook screen or actual customer email.
Confirm the account and sending mode
Record the sender’s own account, the selected From address, client used and whether the permission is Send As or Send on Behalf. Start with one known example and its time and recipient, using appropriate access rather than asking staff to disclose credentials.
Microsoft’s Exchange Online troubleshooting guidance describes a scenario where delegated messages are saved in the sending user’s Sent Items instead of the shared mailbox’s folder. It also documents server-side copy settings for the two sending modes. Verify the tenant’s current configuration before assuming it follows a default.
Agree the required shared record
Ask the mailbox owner which team members need access, which correspondence should appear centrally and how the team handles follow-up. A visible sent copy can help avoid duplicate replies, but it does not assign a conversation owner or create a full case-management process.
The shared-mailbox workflow guide covers broader responsibilities and permissions. This review focuses on the location of copies for newly sent messages, rather than changing the overall mailbox model.
ITZ’s Microsoft 365 administration and support service can assess the copy behaviour alongside staff access. Review Your Shared Mailbox Sent Copies with the affected client and sending mode.
Have an administrator review the matching setting
In Exchange Online, the relevant mailbox properties are MessageCopyForSentAsEnabled and MessageCopyForSendOnBehalfEnabled. An authorised Exchange administrator should inspect their existing values and enable the appropriate server-side copy behaviour when it matches the approved requirement.
Microsoft’s delegated sent-item guidance explains the distinction between the two modes. Avoid applying a client registry workaround without checking the Outlook version; the troubleshooting guidance states that new Outlook uses the server-side method described there.
A settings change is not a retrospective migration of historical messages. If earlier correspondence must be centralised, scope that separately with appropriate permissions, retention considerations and a duplicate-aware copying plan.
Run a small authorised verification
- Use an approved test recipient and a unique, non-sensitive subject; record the sending client and From identity.
- Verify the recipient’s receipt independently from where sent copies appear.
- Check the sender’s personal folder and the shared folder using the intended staff access.
- Repeat the sending modes and clients the team actually uses, including web access where relevant.
- Check that a second authorised colleague can find the shared copy, and document any duplicate copies or synchronisation delay.
Do not expand mailbox permissions merely to make a test easier. If the message itself is missing or delivery is disputed, use a separate message-trace investigation. A sent copy is not evidence that the recipient read or even received the message.
Include the setting in support handover
Record the mailbox owner, intended behaviour, approved properties and tested clients. Recheck after a client migration or mailbox reconfiguration. During employee offboarding, consider whether important business correspondence remains only in a departing employee’s personal sent folder before removing access.
Review Your Shared Mailbox Sent Copies
Share the mailbox type, client version and a sanitised description of the missing-copy behaviour. ITZ can discuss configuration, permissions and a controlled verification plan. Review Your Shared Mailbox Sent Copies using the article-specific form below.
Microsoft documentation reviewed on 8 November 2026. No mailbox was accessed or test message sent while preparing this guide.
