diff --git a/smtp/smtp_121_test.go b/smtp/smtp_121_test.go
new file mode 100644
index 0000000..ed722e0
--- /dev/null
+++ b/smtp/smtp_121_test.go
@@ -0,0 +1,59 @@
+// SPDX-FileCopyrightText: Copyright 2010 The Go Authors. All rights reserved.
+// SPDX-FileCopyrightText: Copyright (c) 2022-2023 The go-mail Authors
+//
+// Original net/smtp code from the Go stdlib by the Go Authors.
+// Use of this source code is governed by a BSD-style
+// LICENSE file that can be found in this directory.
+//
+// go-mail specific modifications by the go-mail Authors.
+// Licensed under the MIT License.
+// See [PROJECT ROOT]/LICENSES directory for more information.
+//
+// SPDX-License-Identifier: BSD-3-Clause AND MIT
+
+//go:build go1.21
+// +build go1.21
+
+package smtp
+
+import (
+	"fmt"
+	"os"
+	"strings"
+	"testing"
+
+	"github.com/wneessen/go-mail/log"
+)
+
+func TestClient_SetDebugLog_JSON(t *testing.T) {
+	t.Run("set debug loggging to on should not override logger", func(t *testing.T) {
+		client := &Client{logger: log.NewJSON(os.Stderr, log.LevelDebug)}
+		client.SetDebugLog(true)
+		if !client.debug {
+			t.Fatalf("expected debug log to be true")
+		}
+		if client.logger == nil {
+			t.Fatalf("expected logger to be defined")
+		}
+		if !strings.EqualFold(fmt.Sprintf("%T", client.logger), "*log.JSONlog") {
+			t.Errorf("expected logger to be of type *log.JSONlog, got: %T", client.logger)
+		}
+	})
+}
+
+func TestClient_SetLogger_JSON(t *testing.T) {
+	t.Run("set logger to JSONlog logger", func(t *testing.T) {
+		client := &Client{}
+		client.SetLogger(log.NewJSON(os.Stderr, log.LevelDebug))
+		if !strings.EqualFold(fmt.Sprintf("%T", client.logger), "*log.JSONlog") {
+			t.Errorf("expected logger to be of type *log.JSONlog, got: %T", client.logger)
+		}
+	})
+	t.Run("nil logger should just return and not set/override", func(t *testing.T) {
+		client := &Client{logger: log.NewJSON(os.Stderr, log.LevelDebug)}
+		client.SetLogger(nil)
+		if !strings.EqualFold(fmt.Sprintf("%T", client.logger), "*log.JSONlog") {
+			t.Errorf("expected logger to be of type *log.JSONlog, got: %T", client.logger)
+		}
+	})
+}
diff --git a/smtp/smtp_test.go b/smtp/smtp_test.go
index e10748b..4d6316a 100644
--- a/smtp/smtp_test.go
+++ b/smtp/smtp_test.go
@@ -3140,19 +3140,6 @@ func TestClient_SetDebugLog(t *testing.T) {
 			t.Errorf("expected logger to be of type *log.Stdlog, got: %T", client.logger)
 		}
 	})
-	t.Run("set debug loggging to on should not override logger", func(t *testing.T) {
-		client := &Client{logger: log.NewJSON(os.Stderr, log.LevelDebug)}
-		client.SetDebugLog(true)
-		if !client.debug {
-			t.Fatalf("expected debug log to be true")
-		}
-		if client.logger == nil {
-			t.Fatalf("expected logger to be defined")
-		}
-		if !strings.EqualFold(fmt.Sprintf("%T", client.logger), "*log.JSONlog") {
-			t.Errorf("expected logger to be of type *log.JSONlog, got: %T", client.logger)
-		}
-	})
 	t.Run("set debug logggin to off with no logger defined", func(t *testing.T) {
 		client := &Client{}
 		client.SetDebugLog(false)
@@ -3183,20 +3170,6 @@ func TestClient_SetLogger(t *testing.T) {
 			t.Errorf("expected logger to be of type *log.Stdlog, got: %T", client.logger)
 		}
 	})
-	t.Run("set logger to JSONlog logger", func(t *testing.T) {
-		client := &Client{}
-		client.SetLogger(log.NewJSON(os.Stderr, log.LevelDebug))
-		if !strings.EqualFold(fmt.Sprintf("%T", client.logger), "*log.JSONlog") {
-			t.Errorf("expected logger to be of type *log.JSONlog, got: %T", client.logger)
-		}
-	})
-	t.Run("nil logger should just return and not set/override", func(t *testing.T) {
-		client := &Client{logger: log.NewJSON(os.Stderr, log.LevelDebug)}
-		client.SetLogger(nil)
-		if !strings.EqualFold(fmt.Sprintf("%T", client.logger), "*log.JSONlog") {
-			t.Errorf("expected logger to be of type *log.JSONlog, got: %T", client.logger)
-		}
-	})
 }
 
 func TestClient_SetLogAuthData(t *testing.T) {