feat: Add mailbox recipient limits standardization script

Add new PowerShell script to standardize mailbox recipient limits across tenants.
This script will help enforce consistent recipient limits for mailboxes in the CIPP platform.

Author: Jr7468

Modules/CIPPCore/Public/Standards/Invoke-CIPPStandardMailboxRecipientLimits.ps1

@@ -0,0 +1,87 @@
+function Invoke-CIPPStandardMailboxRecipientLimits {
+    <#
+    .FUNCTIONALITY
+        Internal
+    .COMPONENT
+        (APIName) MailboxRecipientLimits
+    .SYNOPSIS
+        (Label) Set Mailbox Recipient Limits
+    .DESCRIPTION
+        (Helptext) Sets the maximum number of recipients that can be specified in the To, Cc, and Bcc fields of a message for all mailboxes in the tenant.
+        (DocsDescription) This standard configures the recipient limits for all mailboxes in the tenant. The recipient limit determines the maximum number of recipients that can be specified in the To, Cc, and Bcc fields of a message. This helps prevent spam and manage email flow.
+    .NOTES
+        CAT
+            Exchange Standards
+        TAG
+        ADDEDCOMPONENT
+            {"type":"number","name":"standards.MailboxRecipientLimits.RecipientLimit","label":"Recipient Limit","defaultValue":500}
+        IMPACT
+            Low Impact
+        ADDEDDATE
+            2025-05-28
+        POWERSHELLEQUIVALENT
+            Set-Mailbox -RecipientLimits
+        RECOMMENDEDBY
+            "CIPP"
+    #>
+
+    param($Tenant, $Settings)
+
+    # Input validation
+    if ([Int32]$Settings.RecipientLimit -lt 0 -or [Int32]$Settings.RecipientLimit -gt 10000) {
+        Write-LogMessage -API 'Standards' -tenant $Tenant -message 'MailboxRecipientLimits: Invalid RecipientLimit parameter set. Must be between 0 and 10000.' -sev Error
+        return
+    }
+
+    # Get all mailboxes in the tenant
+    $Mailboxes = New-ExoRequest -tenantid $Tenant -cmdlet 'Get-Mailbox' -cmdParams @{ResultSize = 'Unlimited' }
+
+    # Check which mailboxes need to be updated
+    $MailboxesToUpdate = $Mailboxes | Where-Object { $_.RecipientLimits -ne $Settings.RecipientLimit }
+
+    # Remediation
+    if ($Settings.remediate -eq $true) {
+        if ($MailboxesToUpdate.Count -gt 0) {
+            try {
+                foreach ($Mailbox in $MailboxesToUpdate) {
+                    $null = New-ExoRequest -tenantid $Tenant -cmdlet 'Set-Mailbox' -cmdParams @{
+                        Identity        = $Mailbox.Identity
+                        RecipientLimits = $Settings.RecipientLimit
+                    }
+                }
+                Write-LogMessage -API 'Standards' -tenant $Tenant -message "Successfully set recipient limits to $($Settings.RecipientLimit) for $($MailboxesToUpdate.Count) mailboxes" -sev Info
+            }
+            catch {
+                $ErrorMessage = Get-CippException -Exception $_
+                Write-LogMessage -API 'Standards' -tenant $Tenant -message "Could not set recipient limits. $($ErrorMessage.NormalizedError)" -sev Error -LogData $ErrorMessage
+            }
+        }
+        else {
+            Write-LogMessage -API 'Standards' -tenant $Tenant -message "All mailboxes already have the correct recipient limit of $($Settings.RecipientLimit)" -sev Info
+        }
+    }
+
+    # Alert
+    if ($Settings.alert -eq $true) {
+        if ($MailboxesToUpdate.Count -eq 0) {
+            Write-LogMessage -API 'Standards' -tenant $Tenant -message "All mailboxes have the correct recipient limit of $($Settings.RecipientLimit)" -sev Info
+        }
+        else {
+            Write-StandardsAlert -message "Found $($MailboxesToUpdate.Count) mailboxes with incorrect recipient limits" -object $MailboxesToUpdate -tenant $Tenant -standardName 'MailboxRecipientLimits' -standardId $Settings.standardId
+            Write-LogMessage -API 'Standards' -tenant $Tenant -message "Found $($MailboxesToUpdate.Count) mailboxes with incorrect recipient limits" -sev Info
+        }
+    }
+
+    # Report
+    if ($Settings.report -eq $true) {
+        Add-CIPPBPAField -FieldName 'MailboxRecipientLimits' -FieldValue $MailboxesToUpdate -StoreAs json -Tenant $Tenant
+
+        if ($MailboxesToUpdate.Count -eq 0) {
+            $FieldValue = $true
+        }
+        else {
+            $FieldValue = $MailboxesToUpdate
+        }
+        Set-CIPPStandardsCompareField -FieldName 'standards.MailboxRecipientLimits' -FieldValue $FieldValue -Tenant $Tenant
+    }
+}