Get-ForwardingRules.ps1

<#
    .SYNOPSIS
    Retrieves all Exchange inbox rules that forward messages to another recipient.

    .DESCRIPTION
    Author: James Schlackman <[email protected]>
    Last Modified: Oct 29 2025

    .PARAMETER OutputPath
    Path to optional CSV export file.

    .PARAMETER Recipients
    List of mailbox identities to check for rules. If not specified, all mailboxes in the tenant will be checked.
#>

#Requires -Modules @{ModuleName='ExchangeOnlineManagement'; ModuleVersion='1.0.1'}

Param(
    [Parameter()] [ValidateNotNullOrEmpty()] [String] $OutputPath = ('{0:yyMMdd} Forwarded Mailboxes.csv' -f (Get-Date)),
    [String[]] $Recipients
)

If (!$Recipients) {
    Write-Host 'Getting list of recipients...'
    $Recipients = (Get-EXOMailbox -ResultSize Unlimited).PrimarySmtpAddress | Sort-Object
}

Write-Host ('Number of mailboxes to be checked for forwarding rules: {0}' -f @($Recipients).Count)

$InboxRules = @()

$ProgressPreference = 'Continue'
$progActivity = 'Retrieving mailbox rules'

# Get rules for each mailbox
for ($index = 0; $index -lt @($Recipients).Count; $index++) {

    $rcpt = @($Recipients)[$index]

    Write-Progress -Activity $progActivity -Status $rcpt -PercentComplete ($index * 100 / @($Recipients).Count)
    $InboxRules += Get-InboxRule -Mailbox $rcpt | Select @{Name='Mailbox';Expr={$rcpt}},Name,Enabled,ForwardTo,ForwardAsAttachmentTo,RuleIdentity

}

Write-Progress -Completed

# Filter only rules that have forwards
$resultOutput = $InboxRules | Where-Object {($_.ForwardTo -ne $null) -or ($_.ForwardAsAttachmentTo -ne $null)}

# Show in grid
Write-Host 'See grid export for details and select records for export.'
$resultExport = $resultOutput | Out-GridView -OutputMode Multiple -Title 'Select records for export to CSV'

# Export selected records to file
If ($resultExport) {
    Write-Host 'Exporting to ' -NoNewline
    Write-Host $OutputPath -ForegroundColor Green
    $resultExport | Export-Csv -NoTypeInformation -Path $OutputPath -Encoding UTF8
}