diff --git a/SMTPGraphRelay.ps1 b/SMTPGraphRelay.ps1
index d990ad6..c92bd10 100644
--- a/SMTPGraphRelay.ps1
+++ b/SMTPGraphRelay.ps1
@@ -1,4 +1,4 @@
-[CmdletBinding()]
+[CmdletBinding()]
 param([string]$ConfigPath = "$PSScriptRoot\config.json");
 
 #Requires -Version 5.1
@@ -1160,9 +1160,41 @@ function Get-RelayCertificateStatus {
     };
 }
 
+function Send-CertificateAlertMail {
+    param([Parameter(Mandatory)][int]$DaysRemaining, [Parameter(Mandatory)][string]$Thumbprint);
+
+    $alertMailbox =$null;
+    if ($script:Config.Graph.PSObject.Properties.Name -contains "AlertMailbox") { $alertMailbox = [string]$script:Config.Graph.AlertMailbox; }
+    if ([string]::IsNullOrWhiteSpace($alertMailbox)) { return; }
+
+    $dirs = Get-QueueDirectories;
+    $queueId = New-QueueId;
+    $subject = "WICHTIG: SMTPGraphRelay Zertifikat laeuft ab ($env:COMPUTERNAME)";
+    $body = "Hallo,`r`n`r`ndas Microsoft Graph Zertifikat ($Thumbprint) auf dem Server $env:COMPUTERNAME laeuft in$DaysRemaining Tagen ab.`r`n`r`nBitte das Setup-Skript (Setup-SMTPGraphRelay.ps1) starten und Modus [5] (Zertifikat erneuern) ausfuehren, damit der Mailversand nicht unterbrochen wird.`r`n`r`nViele Gruesse,`r`nSMTPGraphRelay";
+    
+    $lines = New-Object System.Collections.Generic.List[string];$lines.Add("From: <$($script:Config.Graph.SenderMailbox)>");
+    $lines.Add("To: <$alertMailbox>");
+    $lines.Add("Subject: $subject");
+    $lines.Add("MIME-Version: 1.0");
+    $lines.Add("Content-Type: text/plain; charset=utf-8");
+    $lines.Add("");
+    $lines.Add($body);
+    
+    $meta = [ordered]@{ QueueId =$queueId; ReceivedUtc = [DateTime]::UtcNow.ToString("o"); RemoteAddress = "127.0.0.1"; AuthenticatedUser = "SystemAlert"; EnvelopeFrom = $script:Config.Graph.SenderMailbox; EnvelopeRecipients = @($alertMailbox); RetryCount = 0; NextAttemptUtc = [DateTime]::UtcNow.ToString("o"); };
+    
+    $pendingEml = Join-Path ($dirs.Pending) "$queueId.eml";
+    $pendingMeta = "$pendingEml.json";
+    
+    try {
+        $raw = ($lines -join "`r`n") + "`r`n";
+        [IO.File]::WriteAllText($pendingEml,$raw, [System.Text.Encoding]::UTF8);
+        $meta \vert{} ConvertTo-Json -Depth 5 \vert{} Set-Content -LiteralPath ($pendingMeta) -Encoding UTF8;
+        Write-Log "Zertifikats-Warnmail an $alertMailbox in die Queue gelegt (QueueID:$queueId)." "INFO";
+    } catch { Write-Log "Fehler beim Erstellen der Warnmail: $($_.Exception.Message)" "ERROR"; }
+}
+
 function Test-RelayCertificateExpiry {
     param([switch]$ForceLog);
-
     try {
         $status = Get-RelayCertificateStatus;
         $warningDays = 60;
@@ -1173,22 +1205,23 @@ function Test-RelayCertificateExpiry {
 
         if ($status.Expired) {
             Write-Log ("KRITISCH: Graph-Zertifikat {0} ist seit {1} abgelaufen!" -f $status.Thumbprint, $status.NotAfter.ToString("yyyy-MM-dd HH:mm:ss")) "ERROR";
-            return $status;
-        }
-
-        if ($status.DaysRemaining -le $criticalDays) {
+        } elseif ($status.DaysRemaining -le$criticalDays) {
             Write-Log ("KRITISCH: Graph-Zertifikat laeuft in {0} Tagen ab ({1}). Bitte Zertifikat erneuern." -f $status.DaysRemaining, $status.NotAfter.ToString("yyyy-MM-dd HH:mm:ss")) "ERROR";
-        } elseif ($status.DaysRemaining -le $warningDays) {
+        } elseif ($status.DaysRemaining -le$warningDays) {
             Write-Log ("WARNUNG: Graph-Zertifikat laeuft in {0} Tagen ab ({1}). Zertifikatsrotation einplanen." -f $status.DaysRemaining, $status.NotAfter.ToString("yyyy-MM-dd HH:mm:ss")) "WARN";
         } elseif ($ForceLog) {
             Write-Log ("Graph-Zertifikat gueltig bis {0} ({1} Tage verbleibend)." -f $status.NotAfter.ToString("yyyy-MM-dd HH:mm:ss"), $status.DaysRemaining);
         }
 
+        if ($status.DaysRemaining -le $warningDays -and -not$status.Expired) {
+            if (-not $script:LastCertAlert) {$script:LastCertAlert = [DateTime]::MinValue; }
+            if ((Get-Date) -gt $script:LastCertAlert.AddDays(1)) {
+                Send-CertificateAlertMail -DaysRemaining ($status.DaysRemaining) -Thumbprint ($status.Thumbprint);$script:LastCertAlert = Get-Date;
+            }
+        }
+
         return $status;
-    } catch {
-        Write-Log ("Zertifikatspruefung fehlgeschlagen: {0}" -f $_.Exception.Message) "ERROR";
-        return $null;
-    }
+    } catch { Write-Log ("Zertifikatspruefung fehlgeschlagen: {0}" -f $_.Exception.Message) "ERROR"; return $null; }
 }
 
 function Get-FunctionBootstrap {