Send from a Shared Mailbox and Keep Sent Items in the Shared Mailbox (Microsoft 365)

By default, when you send email from a shared mailbox, the sent message lands in YOUR Sent Items folder, not the shared mailbox's Sent Items. This is annoying and defeats the purpose of a shared mailbox where everyone needs visibility.

Here's how to fix it.

The Problem

User sends email as [email protected] (shared mailbox). The sent email appears in the user's personal Sent Items folder. Other users with access to the shared mailbox can't see what was sent. Everyone's confused about who replied to what.

The Fix: Exchange Online PowerShell

This is a mailbox-level setting. You change it once and it applies to everyone sending from that shared mailbox.

Connect to Exchange Online

# Install module if needed
Install-Module -Name ExchangeOnlineManagement

# Connect
Connect-ExchangeOnline -UserPrincipalName [email protected]

Set the Shared Mailbox to Copy Sent Items

Set-Mailbox "[email protected]" -MessageCopyForSentAsEnabled $true

That's it. Emails sent "as" the shared mailbox now copy to the shared mailbox's Sent Items.

If Users Send "On Behalf Of"

There are two ways to send from a shared mailbox:

• Send As: Email appears to come directly from [email protected] (no indication someone else sent it)
• Send on Behalf: Email shows "User Name on behalf of [email protected]"

If your users have "Send on Behalf" permissions instead of (or in addition to) "Send As," you need this setting too:

Set-Mailbox "[email protected]" -MessageCopyForSendOnBehalfEnabled $true

Enable Both (Recommended)

Just run both to cover all cases:

Set-Mailbox "[email protected]" -MessageCopyForSentAsEnabled $true -MessageCopyForSendOnBehalfEnabled $true

Verify Settings

Get-Mailbox "[email protected]" | Select-Object MessageCopyForSentAsEnabled, MessageCopyForSendOnBehalfEnabled

Should return:

MessageCopyForSentAsEnabled    MessageCopyForSendOnBehalfEnabled
---------------------------    ---------------------------------
True                           True

Bulk Update All Shared Mailboxes

If you have multiple shared mailboxes and want to fix them all:

Get-Mailbox -RecipientTypeDetails SharedMailbox | Set-Mailbox -MessageCopyForSentAsEnabled $true -MessageCopyForSendOnBehalfEnabled $true

Alternative: Microsoft 365 Admin Center (GUI)

Microsoft finally added this to the admin center:

1. Go to Microsoft 365 Admin Center → Teams & groups → Shared mailboxes
2. Click on the shared mailbox
3. Under Sent items, click Edit
4. Check both boxes:
   • "Copy items sent as this mailbox"
   • "Copy items sent on behalf of this mailbox"
5. Save

This does the same thing as the PowerShell commands.

Client-Side Behavior

After enabling this setting:

Outlook Desktop (New and Classic):

• Sent items automatically appear in shared mailbox's Sent Items
• May also appear in user's personal Sent Items (depends on Outlook version/settings)
• No client configuration needed

Outlook on the Web (OWA):

• Works automatically
• Sent items appear in shared mailbox

Outlook Mobile:

• Works if shared mailbox is added as a separate account
• If accessing via delegate permissions, behavior may vary

The Duplicate Sent Items Issue

After enabling these settings, some users may see sent emails in BOTH their personal Sent Items AND the shared mailbox's Sent Items.

This is technically correct behavior—the message copies to both places. If users complain about duplicates, explain that this ensures shared mailbox visibility while maintaining their personal record.

If they really hate it, they can create an Outlook rule to delete/move items from their personal Sent Items that were sent from the shared mailbox address. But most users just live with it.

Permissions Refresher

For users to send from a shared mailbox, they need one of these permissions:

Send As (most common):

Add-RecipientPermission "[email protected]" -AccessRights SendAs -Trustee "[email protected]"

Send on Behalf:

Set-Mailbox "[email protected]" -GrantSendOnBehalfTo "[email protected]"

Full Access (to see the mailbox):

Add-MailboxPermission "[email protected]" -User "[email protected]" -AccessRights FullAccess -AutoMapping $true

Most shared mailbox setups need Full Access + Send As.

Troubleshooting

Setting enabled but sent items still going to personal folder:

• Wait 15-30 minutes for changes to propagate
• Have user close and reopen Outlook
• Verify with Get-Mailbox that settings are actually enabled
• Check if user is sending "As" or "On Behalf" and enable the correct setting

User doesn't see the shared mailbox at all:

• Verify Full Access permission is granted
• If AutoMapping is disabled, user needs to manually add the mailbox
• Check in OWA first (eliminates Outlook caching issues)

Outlook shows shared mailbox but no Sent Items folder:

• Expand the shared mailbox in the folder pane
• Sent Items folder should be there—if not, permissions issue
• Try removing and re-adding the shared mailbox in Outlook

Quick Reference

# Connect
Connect-ExchangeOnline

# Fix one shared mailbox
Set-Mailbox "[email protected]" -MessageCopyForSentAsEnabled $true -MessageCopyForSendOnBehalfEnabled $true

# Fix all shared mailboxes
Get-Mailbox -RecipientTypeDetails SharedMailbox | Set-Mailbox -MessageCopyForSentAsEnabled $true -MessageCopyForSendOnBehalfEnabled $true

# Verify
Get-Mailbox "[email protected]" | FL MessageCopy*

# Disconnect when done
Disconnect-ExchangeOnline

This is one of those settings that should be the default but isn't. Set it once when you create the shared mailbox and users never have to think about it.