How to Save Sent Items in Shared Mailbox with PowerShell

First, check if the ExchangeOnlineManagement module is already installed on your system. This module provides the necessary cmdlets to manage Exchange Online settings.

Get-Module -ListAvailable ExchangeOnlineManagement

If the module isn't installed, open PowerShell as Administrator and install it:

Install-Module -Name ExchangeOnlineManagement -Force -AllowClobber

Import the module into your current session:

Import-Module ExchangeOnlineManagement

Establish a connection to your Exchange Online tenant using modern authentication. Replace the email address with your admin account:

Connect-ExchangeOnline -UserPrincipalName admin@contoso.com

This command will prompt for multi-factor authentication if enabled on your account. The connection uses OAuth 2.0 for secure authentication.

Before making changes, identify which shared mailboxes need configuration. List all shared mailboxes in your organization:

Get-Mailbox -ResultSize Unlimited -RecipientTypeDetails SharedMailbox | Select-Object DisplayName, UserPrincipalName, MessageCopyForSentAsEnabled, MessageCopyForSendOnBehalfEnabled

This command shows the current state of the sent item copy settings. Look for mailboxes where both MessageCopyForSentAsEnabled and MessageCopyForSendOnBehalfEnabled are False.

To check a specific shared mailbox:

Get-Mailbox -Identity "shared@contoso.com" | Select-Object DisplayName, MessageCopyForSentAsEnabled, MessageCopyForSendOnBehalfEnabled

Enable sent item copying for a specific shared mailbox. This configuration affects both "Send As" and "Send On Behalf Of" scenarios:

# Enable for Send As permissions
Set-Mailbox -Identity "shared@contoso.com" -MessageCopyForSentAsEnabled $true

# Enable for Send On Behalf Of permissions
Set-Mailbox -Identity "shared@contoso.com" -MessageCopyForSendOnBehalfEnabled $true

Replace "shared@contoso.com" with your actual shared mailbox address. You can use the UserPrincipalName, alias, or display name as the identity.

For convenience, you can set both parameters in a single command:

Set-Mailbox -Identity "shared@contoso.com" -MessageCopyForSentAsEnabled $true -MessageCopyForSendOnBehalfEnabled $true

To enable sent item copying for all shared mailboxes in your organization, use this bulk operation script:

Get-Mailbox -ResultSize Unlimited -RecipientTypeDetails SharedMailbox | ForEach-Object { 
    Write-Host "Configuring: $($_.DisplayName)" -ForegroundColor Green
    Set-Mailbox -Identity $_.UserPrincipalName -MessageCopyForSendOnBehalfEnabled $true -MessageCopyForSentAsEnabled $true -ErrorAction SilentlyContinue
}

This script processes each shared mailbox individually and includes error handling to continue if one mailbox fails. The Write-Host command provides progress feedback.

For organizations with many shared mailboxes, you might want to add a progress counter:

$SharedMailboxes = Get-Mailbox -ResultSize Unlimited -RecipientTypeDetails SharedMailbox
$Counter = 0

$SharedMailboxes | ForEach-Object {
    $Counter++
    Write-Progress -Activity "Configuring Shared Mailboxes" -Status "Processing $($_.DisplayName)" -PercentComplete (($Counter / $SharedMailboxes.Count) * 100)
    Set-Mailbox -Identity $_.UserPrincipalName -MessageCopyForSendOnBehalfEnabled $true -MessageCopyForSentAsEnabled $true
}

For the sent item copying to work properly, users must have the correct permissions on the shared mailbox. Check existing permissions:

# Check Send As permissions
Get-RecipientPermission -Identity "shared@contoso.com" | Where-Object {$_.Trustee -ne "NT AUTHORITY\SELF"} | Select-Object Trustee, AccessRights

# Check Send On Behalf Of permissions
Get-Mailbox -Identity "shared@contoso.com" | Select-Object GrantSendOnBehalfTo

If users need Send As permissions, grant them using:

Add-RecipientPermission -Identity "shared@contoso.com" -Trustee "user@contoso.com" -AccessRights SendAs -Confirm:$false

For Send On Behalf Of permissions:

Set-Mailbox -Identity "shared@contoso.com" -GrantSendOnBehalfTo @{Add="user@contoso.com"}

To add multiple users to Send On Behalf Of:

Set-Mailbox -Identity "shared@contoso.com" -GrantSendOnBehalfTo @{Add="user1@contoso.com","user2@contoso.com"}

After configuration, test that sent items are properly saved to the shared mailbox. The changes may take up to 60 minutes to replicate fully across Exchange Online.

First, check the replication status by re-running the configuration check:

Get-Mailbox -Identity "shared@contoso.com" | Select-Object DisplayName, MessageCopyForSentAsEnabled, MessageCopyForSendOnBehalfEnabled

To test the functionality:

1. Have a user with Send As or Send On Behalf Of permissions open Outlook
2. Compose a new email using the shared mailbox as the "From" address
3. Send the email to a test recipient
4. Check both the user's personal Sent Items and the shared mailbox's Sent Items folder

The email should appear in both locations when the configuration is working correctly.

For troubleshooting, you can also check the message trace:

Get-MessageTrace -SenderAddress "shared@contoso.com" -StartDate (Get-Date).AddHours(-2) -EndDate (Get-Date)

Create a monitoring script to regularly check that your shared mailbox configurations remain correct. Save this script and run it periodically:

# Shared Mailbox Sent Items Configuration Report
$Report = @()
$SharedMailboxes = Get-Mailbox -ResultSize Unlimited -RecipientTypeDetails SharedMailbox

foreach ($Mailbox in $SharedMailboxes) {
    $Report += [PSCustomObject]@{
        DisplayName = $Mailbox.DisplayName
        UserPrincipalName = $Mailbox.UserPrincipalName
        SendAsEnabled = $Mailbox.MessageCopyForSentAsEnabled
        SendOnBehalfEnabled = $Mailbox.MessageCopyForSendOnBehalfEnabled
        ConfigurationStatus = if ($Mailbox.MessageCopyForSentAsEnabled -and $Mailbox.MessageCopyForSendOnBehalfEnabled) { "Configured" } else { "Needs Configuration" }
    }
}

$Report | Format-Table -AutoSize
$Report | Export-Csv -Path "C:\Temp\SharedMailboxConfig_$(Get-Date -Format 'yyyyMMdd').csv" -NoTypeInformation

This script generates both a console display and a CSV file for record-keeping. Schedule it to run monthly to catch any configuration drift.

To fix any mailboxes that show "Needs Configuration":

$Report | Where-Object {$_.ConfigurationStatus -eq "Needs Configuration"} | ForEach-Object {
    Write-Host "Fixing: $($_.DisplayName)" -ForegroundColor Yellow
    Set-Mailbox -Identity $_.UserPrincipalName -MessageCopyForSentAsEnabled $true -MessageCopyForSendOnBehalfEnabled $true
}

Always properly disconnect from Exchange Online when finished to free up connection resources and maintain security best practices:

Disconnect-ExchangeOnline -Confirm:$false

The -Confirm:$false parameter skips the confirmation prompt, making it suitable for automated scripts.

If you want to see the confirmation prompt for manual sessions:

Disconnect-ExchangeOnline

You can also check your current connection status before disconnecting:

Get-ConnectionInformation