<#
.SYNOPSIS
  Audit mailbox delegate access permissions across Exchange environment

.DESCRIPTION
  Reports on SendAs, SendOnBehalf, and FullAccess permissions for all mailboxes.
  Useful for security audits, compliance reviews, and migration planning.

.PARAMETER OutputFolder
  Destination folder for CSV reports. Default: .\MailboxPermissions-<date>

.PARAMETER MailboxFilter
  Optional filter for specific mailboxes. Default: all on-premises mailboxes

.PARAMETER IncludeInherited
  Include inherited permissions in the report (default: $false)

.NOTES
  ⚠️  AI-GENERATED SCRIPT - UNTESTED
  This script was generated by Claude AI and has not been tested in production.
  Review and test thoroughly in a non-production environment before use.

  - Run in Exchange Management Shell with appropriate RBAC permissions
  - Can take significant time with large mailbox counts
  - Tested compatibility: Exchange 2013/2016/2019 (not validated)

.EXAMPLE
  .\Get-MailboxPermissions.ps1

.EXAMPLE
  .\Get-MailboxPermissions.ps1 -OutputFolder "D:\Reports\Permissions" -IncludeInherited $true
#>

[CmdletBinding()]
param(
    [string]$OutputFolder = (Join-Path -Path (Get-Location) -ChildPath ("MailboxPermissions-" + (Get-Date -Format "yyyyMMdd-HHmm"))),
    [string]$MailboxFilter = "*",
    [bool]$IncludeInherited = $false
)

function NowTag { (Get-Date).ToString("yyyy-MM-dd HH:mm:ss") }

Write-Host "[$(NowTag)] ⚠️  AI-GENERATED SCRIPT - UNTESTED" -ForegroundColor Yellow
Write-Host "[$(NowTag)] Starting mailbox permissions audit..." -ForegroundColor Green

# Create output folder
New-Item -ItemType Directory -Path $OutputFolder -Force | Out-Null

# Get all on-premises mailboxes
Write-Host "[$(NowTag)] Retrieving mailboxes..."
$mailboxes = Get-Mailbox -Filter $MailboxFilter -ResultSize Unlimited -ErrorAction SilentlyContinue |
    Where-Object { $_.RecipientTypeDetails -notmatch "^Remote" -and $_.Database }

$mbCount = ($mailboxes | Measure-Object).Count
Write-Host "[$(NowTag)] Found $mbCount mailboxes to audit"

# Collections
$fullAccessPerms = @()
$sendAsPerms = @()
$sendOnBehalfPerms = @()

$current = 0
foreach ($mb in $mailboxes) {
    $current++
    $pct = [int](($current / $mbCount) * 100)
    Write-Progress -Activity "Auditing Mailbox Permissions" -Status "Processing $($mb.DisplayName) ($current/$mbCount)" -PercentComplete $pct

    # FullAccess permissions
    try {
        $fullAccess = Get-MailboxPermission -Identity $mb.Identity -ErrorAction SilentlyContinue |
            Where-Object {
                $_.User -notlike "NT AUTHORITY\*" -and
                $_.User -notlike "S-1-5-*" -and
                $_.AccessRights -like "*FullAccess*" -and
                ($IncludeInherited -or -not $_.IsInherited)
            }

        foreach ($perm in $fullAccess) {
            $fullAccessPerms += [PSCustomObject]@{
                Mailbox           = $mb.DisplayName
                PrimarySmtpAddress = $mb.PrimarySmtpAddress
                User              = $perm.User
                AccessRights      = ($perm.AccessRights -join ", ")
                IsInherited       = $perm.IsInherited
                Deny              = $perm.Deny
            }
        }
    } catch {
        Write-Host "[$(NowTag)] ERROR getting FullAccess for $($mb.DisplayName): $_" -ForegroundColor Red
    }

    # SendAs permissions
    try {
        $sendAs = Get-ADPermission -Identity $mb.DistinguishedName -ErrorAction SilentlyContinue |
            Where-Object {
                $_.ExtendedRights -like "*Send-As*" -and
                $_.User -notlike "NT AUTHORITY\*" -and
                $_.User -notlike "S-1-5-*" -and
                ($IncludeInherited -or -not $_.IsInherited)
            }

        foreach ($perm in $sendAs) {
            $sendAsPerms += [PSCustomObject]@{
                Mailbox           = $mb.DisplayName
                PrimarySmtpAddress = $mb.PrimarySmtpAddress
                User              = $perm.User
                IsInherited       = $perm.IsInherited
                Deny              = $perm.Deny
            }
        }
    } catch {
        Write-Host "[$(NowTag)] ERROR getting SendAs for $($mb.DisplayName): $_" -ForegroundColor Red
    }

    # SendOnBehalf permissions
    if ($mb.GrantSendOnBehalfTo -and $mb.GrantSendOnBehalfTo.Count -gt 0) {
        foreach ($user in $mb.GrantSendOnBehalfTo) {
            $sendOnBehalfPerms += [PSCustomObject]@{
                Mailbox           = $mb.DisplayName
                PrimarySmtpAddress = $mb.PrimarySmtpAddress
                User              = $user
            }
        }
    }
}

Write-Progress -Activity "Auditing Mailbox Permissions" -Completed

# Export results
Write-Host "[$(NowTag)] Exporting results..."

$fullAccessFile = Join-Path $OutputFolder "FullAccess-Permissions.csv"
$sendAsFile = Join-Path $OutputFolder "SendAs-Permissions.csv"
$sendOnBehalfFile = Join-Path $OutputFolder "SendOnBehalf-Permissions.csv"
$summaryFile = Join-Path $OutputFolder "Permissions-Summary.txt"

if ($fullAccessPerms.Count -gt 0) {
    $fullAccessPerms | Export-Csv -NoTypeInformation -Encoding UTF8 -Path $fullAccessFile
    Write-Host "[$(NowTag)] FullAccess permissions: $fullAccessFile"
} else {
    Write-Host "[$(NowTag)] No FullAccess permissions found"
}

if ($sendAsPerms.Count -gt 0) {
    $sendAsPerms | Export-Csv -NoTypeInformation -Encoding UTF8 -Path $sendAsFile
    Write-Host "[$(NowTag)] SendAs permissions: $sendAsFile"
} else {
    Write-Host "[$(NowTag)] No SendAs permissions found"
}

if ($sendOnBehalfPerms.Count -gt 0) {
    $sendOnBehalfPerms | Export-Csv -NoTypeInformation -Encoding UTF8 -Path $sendOnBehalfFile
    Write-Host "[$(NowTag)] SendOnBehalf permissions: $sendOnBehalfFile"
} else {
    Write-Host "[$(NowTag)] No SendOnBehalf permissions found"
}

# Summary
$summary = @"
Mailbox Permissions Audit Summary
Generated: $(Get-Date)

Mailboxes Audited: $mbCount
FullAccess Permissions: $($fullAccessPerms.Count)
SendAs Permissions: $($sendAsPerms.Count)
SendOnBehalf Permissions: $($sendOnBehalfPerms.Count)

Output Folder: $OutputFolder
"@

$summary | Out-File -FilePath $summaryFile -Encoding UTF8
Write-Host "`n$summary"
Write-Host "[$(NowTag)] Audit complete!" -ForegroundColor Green