Quick reference: Which cmdlet does what?

For a shared mailbox:

• Full Access → Add-MailboxPermission
• Send As → Add-RecipientPermission
• (Optional) Send on Behalf → Set-Mailbox -GrantSendOnBehalfTo

You want a script that:

• Takes one shared mailbox
• Adds:
  • A list of users with Full Access
  • A list of users with Send As

Here are:

1. A simple, direct script for a single mailbox
2. A reusable function you can use for multiple mailboxes and run with -WhatIf

1. Simple Script for One Shared Mailbox

#--------------------------------------------------
# Prerequisites
#--------------------------------------------------
# Requires: ExchangeOnlineManagement module
# Install-Module -Name ExchangeOnlineManagement -Scope CurrentUser
# Connect-ExchangeOnline -UserPrincipalName [email protected]

#--------------------------------------------------
# Configuration
#--------------------------------------------------

# Shared mailbox (alias, primary SMTP, or UPN)
$SharedMailbox  = "[email protected]"

# Users who should have Full Access
$FullAccessUsers = @(
    "[email protected]",
    "[email protected]"
)

# Users who should have Send As
$SendAsUsers = @(
    "[email protected]",
    "[email protected]"
)

#--------------------------------------------------
# Script Logic
#--------------------------------------------------

foreach ($user in $FullAccessUsers) {
    try {
        Write-Host "Granting FULL ACCESS on '$SharedMailbox' to '$user'..." -ForegroundColor Cyan

        Add-MailboxPermission -Identity $SharedMailbox `
                              -User $user `
                              -AccessRights FullAccess `
                              -InheritanceType All `
                              -AutoMapping:$true `
                              -ErrorAction Stop

        Write-Host "Full Access granted to '$user' on '$SharedMailbox'." -ForegroundColor Green
    }
    catch {
        Write-Host "Error granting Full Access to '$user' on '$SharedMailbox': $($PSItem.Exception.Message)" -ForegroundColor Red
    }
}

foreach ($user in $SendAsUsers) {
    try {
        Write-Host "Granting SEND AS on '$SharedMailbox' to '$user'..." -ForegroundColor Cyan

        Add-RecipientPermission -Identity $SharedMailbox `
                                -Trustee $user `
                                -AccessRights SendAs `
                                -Confirm:$false `
                                -ErrorAction Stop

        Write-Host "Send As granted to '$user' on '$SharedMailbox'." -ForegroundColor Green
    }
    catch {
        Write-Host "Error granting Send As to '$user' on '$SharedMailbox': $($PSItem.Exception.Message)" -ForegroundColor Red
    }
}
Code language: PHP (php)

Note:

• -AutoMapping:$true (Exchange Online) will auto-add the shared mailbox in Outlook for Full Access users.
• Add-RecipientPermission doesn’t have -WhatIf, so be sure your lists are correct before running.

2. Reusable Function: Add Delegates to Shared Mailbox

Here’s a more “production-worthy” version you can drop into your toolbox. It supports:

• -WhatIf and -Confirm
• Multiple shared mailboxes
• Separate lists of Full Access and Send As users

function Set-SharedMailboxDelegates {
    <#
    .SYNOPSIS
    Adds Full Access and Send As delegates to one or more shared mailboxes.

    .DESCRIPTION
    For each shared mailbox specified, this function:
    - Grants Full Access to the users in -FullAccessUsers
    - Grants Send As to the users in -SendAsUsers

    It uses Add-MailboxPermission for Full Access and Add-RecipientPermission for Send As.

    .PARAMETER SharedMailboxes
    One or more shared mailbox identities (alias, UPN, or primary SMTP).

    .PARAMETER FullAccessUsers
    One or more users who should receive Full Access.

    .PARAMETER SendAsUsers
    One or more users who should receive Send As permission.

    .EXAMPLE
    Set-SharedMailboxDelegates -SharedMailboxes "shared1@yourdomain.com" `
        -FullAccessUsers "user1@yourdomain.com","user2@yourdomain.com" `
        -SendAsUsers "user1@yourdomain.com" -WhatIf

    .EXAMPLE
    Set-SharedMailboxDelegates -SharedMailboxes "shared1@yourdomain.com","shared2@yourdomain.com" `
        -FullAccessUsers "group1@yourdomain.com" `
        -SendAsUsers "user3@yourdomain.com"
    #>

    [CmdletBinding(SupportsShouldProcess)]
    param(
        [Parameter(Mandatory, ValueFromPipeline)]
        [string[]]$SharedMailboxes,

        [Parameter(Mandatory)]
        [string[]]$FullAccessUsers,

        [Parameter(Mandatory)]
        [string[]]$SendAsUsers
    )

    begin {
        Write-Verbose "Ensure you are connected to Exchange Online: Connect-ExchangeOnline"
    }

    process {
        foreach ($shared in $SharedMailboxes) {
            Write-Host "Processing shared mailbox: $shared" -ForegroundColor Yellow

            # --- Full Access Delegates ---
            foreach ($user in $FullAccessUsers) {
                if ($PSCmdlet.ShouldProcess("$shared", "Grant Full Access to $user")) {
                    try {
                        $params = @{
                            Identity        = $shared
                            User            = $user
                            AccessRights    = 'FullAccess'
                            InheritanceType = 'All'
                            AutoMapping     = $true
                            ErrorAction     = 'Stop'
                        }

                        Add-MailboxPermission @params
                        Write-Host "Full Access granted: $user -> $shared" -ForegroundColor Green
                    }
                    catch {
                        Write-Host "Error granting Full Access ($user -> $shared): $($PSItem.Exception.Message)" -ForegroundColor Red
                    }
                }
            }

            # --- Send As Delegates ---
            foreach ($user in $SendAsUsers) {
                if ($PSCmdlet.ShouldProcess("$shared", "Grant Send As to $user")) {
                    try {
                        $params = @{
                            Identity      = $shared
                            Trustee       = $user
                            AccessRights  = 'SendAs'
                            Confirm       = $false
                            ErrorAction   = 'Stop'
                        }

                        Add-RecipientPermission @params
                        Write-Host "Send As granted: $user -> $shared" -ForegroundColor Green
                    }
                    catch {
                        Write-Host "Error granting Send As ($user -> $shared): $($PSItem.Exception.Message)" -ForegroundColor Red
                    }
                }
            }
        }
    }
}Code language: HTML, XML (xml)

Example usage

# Once per session
Import-Module ExchangeOnlineManagement
Connect-ExchangeOnline -UserPrincipalName [email protected]

# Define your mailbox(es) and delegates
$sharedMailboxes = @(
    "[email protected]",
    "[email protected]"
)

$fullAccessUsers = @(
    "[email protected]",
    "[email protected]"
)

$sendAsUsers = @(
    "[email protected]",
    "[email protected]"
)

# Dry-run check
Set-SharedMailboxDelegates -SharedMailboxes $sharedMailboxes `
    -FullAccessUsers $fullAccessUsers `
    -SendAsUsers $sendAsUsers `
    -WhatIf

# Real run
Set-SharedMailboxDelegates -SharedMailboxes $sharedMailboxes `
    -FullAccessUsers $fullAccessUsers `
    -SendAsUsers $sendAsUsersCode language: PHP (php)

Bonus: If you also need “Send on Behalf”

Sometimes shared mailboxes in healthcare workflows need Send on Behalf instead of or in addition to Send As. That uses:

Set-Mailbox -Identity $SharedMailbox -GrantSendOnBehalfTo @{add="[email protected]","[email protected]"}Code language: JavaScript (javascript)

Frank Robinson

Systems Engineer at KnuckleDust Chronicles & FMR Digital LLC

I’m Frank Robinson, a systems engineer, home lab addict, AI music nerd, mover of heavy ass weight and professional overbuilder of ideas.

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