PowerShell Script to Convert Shared Mailbox or User Mailbox with Delegates into Distribution Group

Exchange PFE Daya Patil shares with us a recent script she wrote to help convert a shared mailbox with delegates into a distribution group and preserving the

When working on a recent case, One of our customers needed a quick way to convert their existing shared mailboxes with multiple delegates to a Distribution group.

We made a script to get this done quickly and efficiently.

You can use the script below to convert either a user mailbox or a shared mailbox to Distribution Group.

To delete an existing mailbox and replace it with Distribution group the below syntax can be used, where the owner of the new group is specified.

MBX-To-DG -UserMBX <Mailbox Name> -DGOwner <UserAccount>


As always, please test and fully validate the script prior to running in a production environment.

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Function Mbx-To-DG




Convert a mailbox with multiple Delegates into Distribution Group


This function will Convert a mailbox with multiple Delegates into Distribution Group


The user mailbox with multiple delegates.


The Owner for a distribution group.


The name for distribution group. If you do not specify the name, it would delete your user/shared mailbox and use the name and SMTP address of that mailbox.


To delete existing mailbox and replace it with Distribution group

MBX-To-DG - UserMBX <Mailbox Name> -DGOwner <UserAccount>

To keep existing mailbox and create new Distribution Group with same members and extended rights

MBX-To-DG - UserMBX <Mailbox Name> -DGOwner <UserAccount> -DGName MYDGGroup










$ErrorActionpreference = "SilentlyContinue"

# Getting the mailbox you mentioned

$MBX = Get-Mailbox -Identity $UserMBX -ErrorAction Continue

if (!$MBX) { Write-Error "Mailbox $Mbx not found" -ErrorAction Stop }

# Getting the Delegates for the mailbox

$MBXDelegates = Get-MailboxPermission $MBX.UserPrincipalName | ? {$_.IsInherited -ne $true -and $_.User -ne "NT AUTHORITY\SELF"}

# Getting the users with Send As permission on the mailbox

$MBXSendAS = Get-Mailbox $MBX.UserPrincipalName| Get-ADPermission | where {($_.ExtendedRights -like “*Send-As*”) -and ($_.IsInherited -eq $false) -and -not ($_.User -like “NT AUTHORITY\SELF”)}

# To check if you want new DG group name or replace Existing one



# Removing the mailbox

Remove-Mailbox $MBX.UserPrincipalName -Confirm:$true

# Create new DG with the same email address and name

$DGroup = New-DistributionGroup -Name $MBX.Name -DisplayName $MBX.DisplayName -ManagedBy $DGOwner -PrimarySmtpAddress $MBX.PrimarySMTPAddress -Alias $MBX.Alias

Set-DistributionGroup $DGroup.Identity -GrantSendOnBehalfTo $MBX.grantsendonbehalfto -MailTip $MBX.MailTip -EmailAddresses $($MBX.EmailAddresses | ? {$_ -notlike "sip:*"})




$DGEmail = $DGName + "@" + ($MBX.PrimarySMTPAddress).Domain

# Create new DG with name provided

$DGroup = New-DistributionGroup -Name $DGNAme -DisplayName $DGNAme -ManagedBy $DGOwner -PrimarySmtpAddress $DGEmail -Alias $DGNAme

Set-DistributionGroup $DGroup.Identity -GrantSendOnBehalfTo $MBX.grantsendonbehalfto -MailTip $MBX.MailTip -EmailAddresses $($DGEmail | ? {$_ -notlike "sip:*"})


# Add member of the DG

foreach ($MBXDelegate in $MBXDelegates)


$Member = split-path ([string]($MBXDelegate.user)) -leaf

Write-host “Adding $member as a member to $DGroup”

Add-DistributionGroupMember -Identity $DGroup.Identity -Member $Member -ErrorAction SilentlyContinue


# Add Send As permissions

foreach ($MBXSend in $MBXSendAS)


$Member = split-path ([string]($MBXSend.user)) -leaf

Write-host “ Adding Extended Rights for $member”

Get-DistributionGroup -Identity $DGroup.Identity | Add-AdPermission –ExtendedRights Send-As –User $Member –AccessRights ExtendedRight }

#Add-RecipientPermission -Identity $DGroup.Identity -Trustee $ MBXSend.Trustee -AccessRights $ MBXSend.AccessRights -Confirm:$false



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Published by MSPFE editor Rhoderick Milne.