diff --git a/overlays/default.nix b/overlays/default.nix
index d5b5aae..d5d37e5 100644
--- a/overlays/default.nix
+++ b/overlays/default.nix
@@ -13,7 +13,10 @@ in
     };
   }));
   # (hopefully) fix systemd journal reading
-  prometheus-postfix-exporter = prev.prometheus-postfix-exporter.overrideAttrs (old: rec {
+  prometheus-postfix-exporter = prev.prometheus-postfix-exporter.overrideAttrs (old: {
+    patches = [
+      ./prometheus-postfix-exporter/0001-cleanup-also-catch-milter-reject.patch
+    ];
     src = fetchFromGitHub {
       owner = "adangel";
       repo = "postfix_exporter";
diff --git a/overlays/prometheus-postfix-exporter/0001-cleanup-also-catch-milter-reject.patch b/overlays/prometheus-postfix-exporter/0001-cleanup-also-catch-milter-reject.patch
new file mode 100644
index 0000000..2b60316
--- /dev/null
+++ b/overlays/prometheus-postfix-exporter/0001-cleanup-also-catch-milter-reject.patch
@@ -0,0 +1,25 @@
+From f4c5dd5628c873981b2d6d6b8f3bbf036b9fd724 Mon Sep 17 00:00:00 2001
+From: Rouven Seifert <rouven.seifert@ifsr.de>
+Date: Thu, 2 May 2024 11:20:27 +0200
+Subject: [PATCH] cleanup: also catch milter-reject
+
+---
+ postfix_exporter.go | 2 ++
+ 1 file changed, 2 insertions(+)
+
+diff --git a/postfix_exporter.go b/postfix_exporter.go
+index f20d99c..676d767 100644
+--- a/postfix_exporter.go
++++ b/postfix_exporter.go
+@@ -335,6 +335,8 @@ func (e *PostfixExporter) CollectFromLogLine(line string) {
+ 				e.cleanupProcesses.Inc()
+ 			} else if strings.Contains(remainder, ": reject: ") {
+ 				e.cleanupRejects.Inc()
++			} else if strings.Contains(remainder, ": milter-reject: ") {
++				e.cleanupRejects.Inc()
+ 			} else {
+ 				e.addToUnsupportedLine(line, subprocess, level)
+ 			}
+-- 
+2.44.0
+