client.go

@@ -996,7 +996,7 @@ func (c *Client) DialWithContext(dialCtx context.Context) error {
 // Returns:
 //   - An error if the disconnection fails; otherwise, returns nil.
 func (c *Client) Close() error {
-	if c.smtpClient == nil || !c.smtpClient.HasConnection() {
+	if !c.smtpClient.HasConnection() {
 		return nil
 	}
 	if err := c.smtpClient.Quit(); err != nil {

client_test.go

@@ -1647,15 +1647,6 @@ func TestClient_Close(t *testing.T) {
 			t.Errorf("close was supposed to fail, but didn't")
 		}
 	})
-	t.Run("close on a nil smtpclient should return nil", func(t *testing.T) {
-		client, err := NewClient(DefaultHost)
-		if err != nil {
-			t.Fatalf("failed to create new client: %s", err)
-		}
-		if err = client.Close(); err != nil {
-			t.Errorf("failed to close the client: %s", err)
-		}
-	})
 }
 
 func TestClient_DialWithContext(t *testing.T) {

doc.go

@@ -11,4 +11,4 @@ package mail
 
 // VERSION indicates the current version of the package. It is also attached to the default user
 // agent string.
-const VERSION = "0.5.2"
+const VERSION = "0.5.1"

smtp/auth_login.go

@@ -36,8 +36,8 @@ type loginAuth struct {
 // LoginAuth will only send the credentials if the connection is using TLS
 // or is connected to localhost. Otherwise authentication will fail with an
 // error, without sending the credentials.
-func LoginAuth(username, password, host string, allowUnenc bool) Auth {
-	return &loginAuth{username, password, host, 0, allowUnenc}
+func LoginAuth(username, password, host string, allowUnEnc bool) Auth {
+	return &loginAuth{username, password, host, 0, allowUnEnc}
 }
 
 // Start begins the SMTP authentication process by validating server's TLS status and hostname.

smtp/auth_plain.go

@@ -28,8 +28,8 @@ type plainAuth struct {
 // PlainAuth will only send the credentials if the connection is using TLS
 // or is connected to localhost. Otherwise authentication will fail with an
 // error, without sending the credentials.
-func PlainAuth(identity, username, password, host string, allowUnenc bool) Auth {
-	return &plainAuth{identity, username, password, host, allowUnenc}
+func PlainAuth(identity, username, password, host string, allowUnEnc bool) Auth {
+	return &plainAuth{identity, username, password, host, allowUnEnc}
 }
 
 func (a *plainAuth) Start(server *ServerInfo) (string, []byte, error) {

smtp/smtp_test.go

@@ -14,69 +14,11 @@
 package smtp
 
 import (
-	"bufio"
 	"bytes"
-	"context"
-	"crypto/tls"
 	"errors"
-	"fmt"
-	"net"
-	"strings"
-	"sync/atomic"
 	"testing"
-	"time"
 )
 
-const (
-	// TestServerProto is the protocol used for the simple SMTP test server
-	TestServerProto = "tcp"
-	// TestServerAddr is the address the simple SMTP test server listens on
-	TestServerAddr = "127.0.0.1"
-	// TestServerPortBase is the base port for the simple SMTP test server
-	TestServerPortBase = 12025
-)
-
-// PortAdder is an atomic counter used to increment port numbers for the test SMTP server instances.
-var PortAdder atomic.Int32
-
-// localhostCert is a PEM-encoded TLS cert generated from src/crypto/tls:
-//
-//	go run generate_cert.go --rsa-bits 1024 --host 127.0.0.1,::1,example.com \
-//		--ca --start-date "Jan 1 00:00:00 1970" --duration=1000000h
-var localhostCert = []byte(`
------BEGIN CERTIFICATE-----
-MIICFDCCAX2gAwIBAgIRAK0xjnaPuNDSreeXb+z+0u4wDQYJKoZIhvcNAQELBQAw
-EjEQMA4GA1UEChMHQWNtZSBDbzAgFw03MDAxMDEwMDAwMDBaGA8yMDg0MDEyOTE2
-MDAwMFowEjEQMA4GA1UEChMHQWNtZSBDbzCBnzANBgkqhkiG9w0BAQEFAAOBjQAw
-gYkCgYEA0nFbQQuOWsjbGtejcpWz153OlziZM4bVjJ9jYruNw5n2Ry6uYQAffhqa
-JOInCmmcVe2siJglsyH9aRh6vKiobBbIUXXUU1ABd56ebAzlt0LobLlx7pZEMy30
-LqIi9E6zmL3YvdGzpYlkFRnRrqwEtWYbGBf3znO250S56CCWH2UCAwEAAaNoMGYw
-DgYDVR0PAQH/BAQDAgKkMBMGA1UdJQQMMAoGCCsGAQUFBwMBMA8GA1UdEwEB/wQF
-MAMBAf8wLgYDVR0RBCcwJYILZXhhbXBsZS5jb22HBH8AAAGHEAAAAAAAAAAAAAAA
-AAAAAAEwDQYJKoZIhvcNAQELBQADgYEAbZtDS2dVuBYvb+MnolWnCNqvw1w5Gtgi
-NmvQQPOMgM3m+oQSCPRTNGSg25e1Qbo7bgQDv8ZTnq8FgOJ/rbkyERw2JckkHpD4
-n4qcK27WkEDBtQFlPihIM8hLIuzWoi/9wygiElTy/tVL3y7fGCvY2/k1KBthtZGF
-tN8URjVmyEo=
------END CERTIFICATE-----`)
-
-// localhostKey is the private key for localhostCert.
-var localhostKey = []byte(testingKey(`
------BEGIN RSA TESTING KEY-----
-MIICXgIBAAKBgQDScVtBC45ayNsa16NylbPXnc6XOJkzhtWMn2Niu43DmfZHLq5h
-AB9+Gpok4icKaZxV7ayImCWzIf1pGHq8qKhsFshRddRTUAF3np5sDOW3QuhsuXHu
-lkQzLfQuoiL0TrOYvdi90bOliWQVGdGurAS1ZhsYF/fOc7bnRLnoIJYfZQIDAQAB
-AoGBAMst7OgpKyFV6c3JwyI/jWqxDySL3caU+RuTTBaodKAUx2ZEmNJIlx9eudLA
-kucHvoxsM/eRxlxkhdFxdBcwU6J+zqooTnhu/FE3jhrT1lPrbhfGhyKnUrB0KKMM
-VY3IQZyiehpxaeXAwoAou6TbWoTpl9t8ImAqAMY8hlULCUqlAkEA+9+Ry5FSYK/m
-542LujIcCaIGoG1/Te6Sxr3hsPagKC2rH20rDLqXwEedSFOpSS0vpzlPAzy/6Rbb
-PHTJUhNdwwJBANXkA+TkMdbJI5do9/mn//U0LfrCR9NkcoYohxfKz8JuhgRQxzF2
-6jpo3q7CdTuuRixLWVfeJzcrAyNrVcBq87cCQFkTCtOMNC7fZnCTPUv+9q1tcJyB
-vNjJu3yvoEZeIeuzouX9TJE21/33FaeDdsXbRhQEj23cqR38qFHsF1qAYNMCQQDP
-QXLEiJoClkR2orAmqjPLVhR3t2oB3INcnEjLNSq8LHyQEfXyaFfu4U9l5+fRPL2i
-jiC0k/9L5dHUsF0XZothAkEA23ddgRs+Id/HxtojqqUT27B8MT/IGNrYsp4DvS/c
-qgkeluku4GjxRlDMBuXk94xOBEinUs+p/hwP1Alll80Tpg==
------END RSA TESTING KEY-----`))
-
 type authTest struct {
 	auth       Auth
 	challenges []string
@@ -360,59 +302,6 @@ func TestPlainAuth(t *testing.T) {
 			t.Errorf("expected error to be: %s, got: %s", ErrUnexpectedServerChallange, err)
 		}
 	})
-	t.Run("PLAIN authentication on test server", func(t *testing.T) {
-		ctx, cancel := context.WithCancel(context.Background())
-		defer cancel()
-		PortAdder.Add(1)
-		serverPort := int(TestServerPortBase + PortAdder.Load())
-		featureSet := "250-AUTH PLAIN\r\n250-8BITMIME\r\n250-DSN\r\n250 SMTPUTF8"
-		go func() {
-			if err := simpleSMTPServer(ctx, t, &serverProps{
-				FeatureSet: featureSet,
-				ListenPort: serverPort},
-			); err != nil {
-				t.Errorf("failed to start test server: %s", err)
-				return
-			}
-		}()
-		time.Sleep(time.Millisecond * 30)
-
-		auth := PlainAuth("", "user", "pass", TestServerAddr, false)
-		client, err := Dial(fmt.Sprintf("%s:%d", TestServerAddr, serverPort))
-		if err != nil {
-			t.Fatalf("failed to connect to test server: %s", err)
-		}
-		if err = client.Auth(auth); err != nil {
-			t.Errorf("failed to authenticate to test server: %s", err)
-		}
-	})
-	t.Run("PLAIN authentication on test server should fail", func(t *testing.T) {
-		ctx, cancel := context.WithCancel(context.Background())
-		defer cancel()
-		PortAdder.Add(1)
-		serverPort := int(TestServerPortBase + PortAdder.Load())
-		featureSet := "250-AUTH PLAIN\r\n250-8BITMIME\r\n250-DSN\r\n250 SMTPUTF8"
-		go func() {
-			if err := simpleSMTPServer(ctx, t, &serverProps{
-				FailOnAuth: true,
-				FeatureSet: featureSet,
-				ListenPort: serverPort},
-			); err != nil {
-				t.Errorf("failed to start test server: %s", err)
-				return
-			}
-		}()
-		time.Sleep(time.Millisecond * 30)
-
-		auth := PlainAuth("", "user", "pass", TestServerAddr, false)
-		client, err := Dial(fmt.Sprintf("%s:%d", TestServerAddr, serverPort))
-		if err != nil {
-			t.Fatalf("failed to connect to test server: %s", err)
-		}
-		if err = client.Auth(auth); err == nil {
-			t.Errorf("expected authentication to fail")
-		}
-	})
 }
 
 func TestPlainAuth_noEnc(t *testing.T) {
@@ -508,350 +397,100 @@ func TestPlainAuth_noEnc(t *testing.T) {
 			t.Errorf("expected error to be: %s, got: %s", ErrUnexpectedServerChallange, err)
 		}
 	})
-	t.Run("PLAIN-NOENC authentication on test server", func(t *testing.T) {
-		ctx, cancel := context.WithCancel(context.Background())
-		defer cancel()
-		PortAdder.Add(1)
-		serverPort := int(TestServerPortBase + PortAdder.Load())
-		featureSet := "250-AUTH PLAIN\r\n250-8BITMIME\r\n250-DSN\r\n250 SMTPUTF8"
-		go func() {
-			if err := simpleSMTPServer(ctx, t, &serverProps{
-				FeatureSet: featureSet,
-				ListenPort: serverPort},
-			); err != nil {
-				t.Errorf("failed to start test server: %s", err)
-				return
-			}
-		}()
-		time.Sleep(time.Millisecond * 30)
-
-		auth := PlainAuth("", "user", "pass", TestServerAddr, true)
-		client, err := Dial(fmt.Sprintf("%s:%d", TestServerAddr, serverPort))
-		if err != nil {
-			t.Fatalf("failed to connect to test server: %s", err)
-		}
-		if err = client.Auth(auth); err != nil {
-			t.Errorf("failed to authenticate to test server: %s", err)
-		}
-	})
-	t.Run("PLAIN-NOENC authentication on test server should fail", func(t *testing.T) {
-		ctx, cancel := context.WithCancel(context.Background())
-		defer cancel()
-		PortAdder.Add(1)
-		serverPort := int(TestServerPortBase + PortAdder.Load())
-		featureSet := "250-AUTH PLAIN\r\n250-8BITMIME\r\n250-DSN\r\n250 SMTPUTF8"
-		go func() {
-			if err := simpleSMTPServer(ctx, t, &serverProps{
-				FailOnAuth: true,
-				FeatureSet: featureSet,
-				ListenPort: serverPort},
-			); err != nil {
-				t.Errorf("failed to start test server: %s", err)
-				return
-			}
-		}()
-		time.Sleep(time.Millisecond * 30)
-
-		auth := PlainAuth("", "user", "pass", TestServerAddr, true)
-		client, err := Dial(fmt.Sprintf("%s:%d", TestServerAddr, serverPort))
-		if err != nil {
-			t.Fatalf("failed to connect to test server: %s", err)
-		}
-		if err = client.Auth(auth); err == nil {
-			t.Errorf("expected authentication to fail")
-		}
-	})
-}
-
-func TestLoginAuth(t *testing.T) {
-	tests := []struct {
-		name       string
-		authName   string
-		server     *ServerInfo
-		shouldFail bool
-		wantErr    error
-	}{
-		{
-			name:       "LOGIN auth succeeds",
-			authName:   "servername",
-			server:     &ServerInfo{Name: "servername", TLS: true},
-			shouldFail: false,
-		},
-		{
-			// OK to use PlainAuth on localhost without TLS
-			name:       "LOGIN on localhost is allowed to go unencrypted",
-			authName:   "localhost",
-			server:     &ServerInfo{Name: "localhost", TLS: false},
-			shouldFail: false,
-		},
-		{
-			// NOT OK on non-localhost, even if server says LOGIN is OK.
-			// (We don't know that the server is the real server.)
-			name:       "LOGIN on non-localhost is not allowed to go unencrypted",
-			authName:   "servername",
-			server:     &ServerInfo{Name: "servername", Auth: []string{"LOGIN"}},
-			shouldFail: true,
-			wantErr:    ErrUnencrypted,
-		},
-		{
-			name:       "LOGIN on non-localhost with no LOGIN announcement, is not allowed to go unencrypted",
-			authName:   "servername",
-			server:     &ServerInfo{Name: "servername", Auth: []string{"CRAM-MD5"}},
-			shouldFail: true,
-			wantErr:    ErrUnencrypted,
-		},
-		{
-			name:       "LOGIN with wrong hostname",
-			authName:   "servername",
-			server:     &ServerInfo{Name: "attacker", TLS: true},
-			shouldFail: true,
-			wantErr:    ErrWrongHostname,
-		},
-	}
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			user := "toni.tester@example.com"
-			pass := "v3ryS3Cur3P4ssw0rd"
-			auth := LoginAuth(user, pass, tt.authName, false)
-			method, _, err := auth.Start(tt.server)
-			if err != nil && !tt.shouldFail {
-				t.Errorf("login authentication failed: %s", err)
-			}
-			if err == nil && tt.shouldFail {
-				t.Error("login authentication was expected to fail")
-			}
-			if tt.wantErr != nil {
-				if !errors.Is(err, tt.wantErr) {
-					t.Errorf("expected error to be: %s, got: %s", tt.wantErr, err)
-				}
-				return
-			}
-			if method != "LOGIN" {
-				t.Errorf("expected method return to be: %q, got: %q", "LOGIN", method)
-			}
-			resp, err := auth.Next([]byte(user), true)
-			if err != nil {
-				t.Errorf("failed on first server challange: %s", err)
-			}
-			if !bytes.Equal([]byte(user), resp) {
-				t.Errorf("expected response to first challange to be: %q, got: %q", user, resp)
-			}
-			resp, err = auth.Next([]byte(pass), true)
-			if err != nil {
-				t.Errorf("failed on second server challange: %s", err)
-			}
-			if !bytes.Equal([]byte(pass), resp) {
-				t.Errorf("expected response to second challange to be: %q, got: %q", pass, resp)
-			}
-			resp, err = auth.Next([]byte("nonsense"), true)
-			if err == nil {
-				t.Error("expected third server challange to fail, but didn't")
-			}
-			if !errors.Is(err, ErrUnexpectedServerResponse) {
-				t.Errorf("expected error to be: %s, got: %s", ErrUnexpectedServerResponse, err)
-			}
-		})
-	}
-	t.Run("LOGIN authentication on test server", func(t *testing.T) {
-		ctx, cancel := context.WithCancel(context.Background())
-		defer cancel()
-		PortAdder.Add(1)
-		serverPort := int(TestServerPortBase + PortAdder.Load())
-		featureSet := "250-AUTH LOGIN\r\n250-8BITMIME\r\n250-DSN\r\n250 SMTPUTF8"
-		go func() {
-			if err := simpleSMTPServer(ctx, t, &serverProps{
-				FeatureSet: featureSet,
-				ListenPort: serverPort},
-			); err != nil {
-				t.Errorf("failed to start test server: %s", err)
-				return
-			}
-		}()
-		time.Sleep(time.Millisecond * 30)
-
-		auth := LoginAuth("user", "pass", TestServerAddr, false)
-		client, err := Dial(fmt.Sprintf("%s:%d", TestServerAddr, serverPort))
-		if err != nil {
-			t.Fatalf("failed to connect to test server: %s", err)
-		}
-		if err = client.Auth(auth); err != nil {
-			t.Errorf("failed to authenticate to test server: %s", err)
-		}
-	})
-	t.Run("LOGIN authentication on test server should fail", func(t *testing.T) {
-		ctx, cancel := context.WithCancel(context.Background())
-		defer cancel()
-		PortAdder.Add(1)
-		serverPort := int(TestServerPortBase + PortAdder.Load())
-		featureSet := "250-AUTH LOGIN\r\n250-8BITMIME\r\n250-DSN\r\n250 SMTPUTF8"
-		go func() {
-			if err := simpleSMTPServer(ctx, t, &serverProps{
-				FailOnAuth: true,
-				FeatureSet: featureSet,
-				ListenPort: serverPort},
-			); err != nil {
-				t.Errorf("failed to start test server: %s", err)
-				return
-			}
-		}()
-		time.Sleep(time.Millisecond * 30)
-
-		auth := LoginAuth("user", "pass", TestServerAddr, false)
-		client, err := Dial(fmt.Sprintf("%s:%d", TestServerAddr, serverPort))
-		if err != nil {
-			t.Fatalf("failed to connect to test server: %s", err)
-		}
-		if err = client.Auth(auth); err == nil {
-			t.Errorf("expected authentication to fail")
-		}
-	})
-}
-
-func TestLoginAuth_noEnc(t *testing.T) {
-	tests := []struct {
-		name       string
-		authName   string
-		server     *ServerInfo
-		shouldFail bool
-		wantErr    error
-	}{
-		{
-			name:       "LOGIN-NOENC auth succeeds",
-			authName:   "servername",
-			server:     &ServerInfo{Name: "servername", TLS: true},
-			shouldFail: false,
-		},
-		{
-			// OK to use PlainAuth on localhost without TLS
-			name:       "LOGIN-NOENC on localhost is allowed to go unencrypted",
-			authName:   "localhost",
-			server:     &ServerInfo{Name: "localhost", TLS: false},
-			shouldFail: false,
-		},
-		{
-			// ALSO OK on non-localhost. This auth mode is specificly for that.
-			name:       "LOGIN-NOENC on non-localhost is allowed to go unencrypted",
-			authName:   "servername",
-			server:     &ServerInfo{Name: "servername", Auth: []string{"LOGIN"}},
-			shouldFail: false,
-		},
-		{
-			name:       "LOGIN-NOENC on non-localhost with no LOGIN announcement, is not allowed to go unencrypted",
-			authName:   "servername",
-			server:     &ServerInfo{Name: "servername", Auth: []string{"CRAM-MD5"}},
-			shouldFail: false,
-		},
-		{
-			name:       "LOGIN-NOENC with wrong hostname",
-			authName:   "servername",
-			server:     &ServerInfo{Name: "attacker", TLS: true},
-			shouldFail: true,
-			wantErr:    ErrWrongHostname,
-		},
-	}
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			user := "toni.tester@example.com"
-			pass := "v3ryS3Cur3P4ssw0rd"
-			auth := LoginAuth(user, pass, tt.authName, true)
-			method, _, err := auth.Start(tt.server)
-			if err != nil && !tt.shouldFail {
-				t.Errorf("login authentication failed: %s", err)
-			}
-			if err == nil && tt.shouldFail {
-				t.Error("login authentication was expected to fail")
-			}
-			if tt.wantErr != nil {
-				if !errors.Is(err, tt.wantErr) {
-					t.Errorf("expected error to be: %s, got: %s", tt.wantErr, err)
-				}
-				return
-			}
-			if method != "LOGIN" {
-				t.Errorf("expected method return to be: %q, got: %q", "LOGIN", method)
-			}
-			resp, err := auth.Next([]byte(user), true)
-			if err != nil {
-				t.Errorf("failed on first server challange: %s", err)
-			}
-			if !bytes.Equal([]byte(user), resp) {
-				t.Errorf("expected response to first challange to be: %q, got: %q", user, resp)
-			}
-			resp, err = auth.Next([]byte(pass), true)
-			if err != nil {
-				t.Errorf("failed on second server challange: %s", err)
-			}
-			if !bytes.Equal([]byte(pass), resp) {
-				t.Errorf("expected response to second challange to be: %q, got: %q", pass, resp)
-			}
-			resp, err = auth.Next([]byte("nonsense"), true)
-			if err == nil {
-				t.Error("expected third server challange to fail, but didn't")
-			}
-			if !errors.Is(err, ErrUnexpectedServerResponse) {
-				t.Errorf("expected error to be: %s, got: %s", ErrUnexpectedServerResponse, err)
-			}
-		})
-	}
-	t.Run("LOGIN-NOENC authentication on test server", func(t *testing.T) {
-		ctx, cancel := context.WithCancel(context.Background())
-		defer cancel()
-		PortAdder.Add(1)
-		serverPort := int(TestServerPortBase + PortAdder.Load())
-		featureSet := "250-AUTH LOGIN\r\n250-8BITMIME\r\n250-DSN\r\n250 SMTPUTF8"
-		go func() {
-			if err := simpleSMTPServer(ctx, t, &serverProps{
-				FeatureSet: featureSet,
-				ListenPort: serverPort},
-			); err != nil {
-				t.Errorf("failed to start test server: %s", err)
-				return
-			}
-		}()
-		time.Sleep(time.Millisecond * 30)
-
-		auth := LoginAuth("user", "pass", TestServerAddr, true)
-		client, err := Dial(fmt.Sprintf("%s:%d", TestServerAddr, serverPort))
-		if err != nil {
-			t.Fatalf("failed to connect to test server: %s", err)
-		}
-		if err = client.Auth(auth); err != nil {
-			t.Errorf("failed to authenticate to test server: %s", err)
-		}
-	})
-	t.Run("LOGIN-NOENC authentication on test server should fail", func(t *testing.T) {
-		ctx, cancel := context.WithCancel(context.Background())
-		defer cancel()
-		PortAdder.Add(1)
-		serverPort := int(TestServerPortBase + PortAdder.Load())
-		featureSet := "250-AUTH LOGIN\r\n250-8BITMIME\r\n250-DSN\r\n250 SMTPUTF8"
-		go func() {
-			if err := simpleSMTPServer(ctx, t, &serverProps{
-				FailOnAuth: true,
-				FeatureSet: featureSet,
-				ListenPort: serverPort},
-			); err != nil {
-				t.Errorf("failed to start test server: %s", err)
-				return
-			}
-		}()
-		time.Sleep(time.Millisecond * 30)
-
-		auth := LoginAuth("user", "pass", TestServerAddr, true)
-		client, err := Dial(fmt.Sprintf("%s:%d", TestServerAddr, serverPort))
-		if err != nil {
-			t.Fatalf("failed to connect to test server: %s", err)
-		}
-		if err = client.Auth(auth); err == nil {
-			t.Errorf("expected authentication to fail")
-		}
-	})
 }
 
 /*
 
 
+func TestAuthLogin(t *testing.T) {
+	tests := []struct {
+		authName string
+		server   *ServerInfo
+		err      string
+	}{
+		{
+			authName: "servername",
+			server:   &ServerInfo{Name: "servername", TLS: true},
+		},
+		{
+			// OK to use LoginAuth on localhost without TLS
+			authName: "localhost",
+			server:   &ServerInfo{Name: "localhost", TLS: false},
+		},
+		{
+			// NOT OK on non-localhost, even if server says PLAIN is OK.
+			// (We don't know that the server is the real server.)
+			authName: "servername",
+			server:   &ServerInfo{Name: "servername", Auth: []string{"LOGIN"}},
+			err:      "unencrypted connection",
+		},
+		{
+			authName: "servername",
+			server:   &ServerInfo{Name: "servername", Auth: []string{"CRAM-MD5"}},
+			err:      "unencrypted connection",
+		},
+		{
+			authName: "servername",
+			server:   &ServerInfo{Name: "attacker", TLS: true},
+			err:      "wrong host name",
+		},
+	}
+	for i, tt := range tests {
+		auth := LoginAuth("foo", "bar", tt.authName, false)
+		_, _, err := auth.Start(tt.server)
+		got := ""
+		if err != nil {
+			got = err.Error()
+		}
+		if got != tt.err {
+			t.Errorf("%d. got error = %q; want %q", i, got, tt.err)
+		}
+	}
+}
 
+func TestAuthLoginNoEnc(t *testing.T) {
+	tests := []struct {
+		authName string
+		server   *ServerInfo
+		err      string
+	}{
+		{
+			authName: "servername",
+			server:   &ServerInfo{Name: "servername", TLS: true},
+		},
+		{
+			// OK to use LoginAuth on localhost without TLS
+			authName: "localhost",
+			server:   &ServerInfo{Name: "localhost", TLS: false},
+		},
+		{
+			// Also OK on non-TLS secured connections. The NoEnc mechanism is meant to allow
+			// non-encrypted connections.
+			authName: "servername",
+			server:   &ServerInfo{Name: "servername", Auth: []string{"LOGIN"}},
+		},
+		{
+			authName: "servername",
+			server:   &ServerInfo{Name: "servername", Auth: []string{"CRAM-MD5"}},
+		},
+		{
+			authName: "servername",
+			server:   &ServerInfo{Name: "attacker", TLS: true},
+			err:      "wrong host name",
+		},
+	}
+	for i, tt := range tests {
+		auth := LoginAuth("foo", "bar", tt.authName, true)
+		_, _, err := auth.Start(tt.server)
+		got := ""
+		if err != nil {
+			got = err.Error()
+		}
+		if got != tt.err {
+			t.Errorf("%d. got error = %q; want %q", i, got, tt.err)
+		}
+	}
+}
 
 func TestXOAuth2OK(t *testing.T) {
 	server := []string{
@@ -3016,229 +2655,3 @@ func startSMTPServer(tlsServer bool, hostname, port string, h func() hash.Hash)
 
 
 */
-// testingKey replaces the substring "TESTING KEY" with "PRIVATE KEY" in the given string s.
-func testingKey(s string) string { return strings.ReplaceAll(s, "TESTING KEY", "PRIVATE KEY") }
-
-// serverProps represents the configuration properties for the SMTP server.
-type serverProps struct {
-	FailOnAuth      bool
-	FailOnDataInit  bool
-	FailOnDataClose bool
-	FailOnHelo      bool
-	FailOnMailFrom  bool
-	FailOnNoop      bool
-	FailOnQuit      bool
-	FailOnReset     bool
-	FailOnSTARTTLS  bool
-	FailTemp        bool
-	FeatureSet      string
-	ListenPort      int
-	SSLListener     bool
-	IsTLS           bool
-	SupportDSN      bool
-}
-
-// simpleSMTPServer starts a simple TCP server that resonds to SMTP commands.
-// The provided featureSet represents in what the server responds to EHLO command
-// failReset controls if a RSET succeeds
-func simpleSMTPServer(ctx context.Context, t *testing.T, props *serverProps) error {
-	t.Helper()
-	if props == nil {
-		return fmt.Errorf("no server properties provided")
-	}
-
-	var listener net.Listener
-	var err error
-	if props.SSLListener {
-		keypair, err := tls.X509KeyPair(localhostCert, localhostKey)
-		if err != nil {
-			return fmt.Errorf("failed to read TLS keypair: %w", err)
-		}
-		tlsConfig := &tls.Config{Certificates: []tls.Certificate{keypair}}
-		listener, err = tls.Listen(TestServerProto, fmt.Sprintf("%s:%d", TestServerAddr, props.ListenPort),
-			tlsConfig)
-		if err != nil {
-			t.Fatalf("failed to create TLS listener: %s", err)
-		}
-	} else {
-		listener, err = net.Listen(TestServerProto, fmt.Sprintf("%s:%d", TestServerAddr, props.ListenPort))
-	}
-	if err != nil {
-		return fmt.Errorf("unable to listen on %s://%s: %w (SSL: %t)", TestServerProto, TestServerAddr, err,
-			props.SSLListener)
-	}
-
-	defer func() {
-		if err := listener.Close(); err != nil {
-			t.Logf("failed to close listener: %s", err)
-		}
-	}()
-
-	for {
-		select {
-		case <-ctx.Done():
-			return nil
-		default:
-			connection, err := listener.Accept()
-			var opErr *net.OpError
-			if err != nil {
-				if errors.As(err, &opErr) && opErr.Temporary() {
-					continue
-				}
-				return fmt.Errorf("unable to accept connection: %w", err)
-			}
-			handleTestServerConnection(connection, t, props)
-		}
-	}
-}
-
-func handleTestServerConnection(connection net.Conn, t *testing.T, props *serverProps) {
-	t.Helper()
-	if !props.IsTLS {
-		t.Cleanup(func() {
-			if err := connection.Close(); err != nil {
-				t.Logf("failed to close connection: %s", err)
-			}
-		})
-	}
-
-	reader := bufio.NewReader(connection)
-	writer := bufio.NewWriter(connection)
-
-	writeLine := func(data string) {
-		_, err := writer.WriteString(data + "\r\n")
-		if err != nil {
-			t.Logf("failed to write line: %s", err)
-		}
-		_ = writer.Flush()
-	}
-	writeOK := func() {
-		writeLine("250 2.0.0 OK")
-	}
-
-	if !props.IsTLS {
-		writeLine("220 go-mail test server ready ESMTP")
-	}
-
-	for {
-		data, err := reader.ReadString('\n')
-		if err != nil {
-			break
-		}
-		time.Sleep(time.Millisecond)
-
-		var datastring string
-		data = strings.TrimSpace(data)
-		switch {
-		case strings.HasPrefix(data, "EHLO"), strings.HasPrefix(data, "HELO"):
-			if len(strings.Split(data, " ")) != 2 {
-				writeLine("501 Syntax: EHLO hostname")
-				break
-			}
-			if props.FailOnHelo {
-				writeLine("500 5.5.2 Error: fail on HELO")
-				break
-			}
-			writeLine("250-localhost.localdomain\r\n" + props.FeatureSet)
-		case strings.HasPrefix(data, "MAIL FROM:"):
-			if props.FailOnMailFrom {
-				writeLine("500 5.5.2 Error: fail on MAIL FROM")
-				break
-			}
-			from := strings.TrimPrefix(data, "MAIL FROM:")
-			from = strings.ReplaceAll(from, "BODY=8BITMIME", "")
-			from = strings.ReplaceAll(from, "SMTPUTF8", "")
-			if props.SupportDSN {
-				from = strings.ReplaceAll(from, "RET=FULL", "")
-			}
-			from = strings.TrimSpace(from)
-			if !strings.EqualFold(from, "<valid-from@domain.tld>") {
-				writeLine(fmt.Sprintf("503 5.1.2 Invalid from: %s", from))
-				break
-			}
-			writeOK()
-		case strings.HasPrefix(data, "RCPT TO:"):
-			to := strings.TrimPrefix(data, "RCPT TO:")
-			if props.SupportDSN {
-				to = strings.ReplaceAll(to, "NOTIFY=FAILURE,SUCCESS", "")
-			}
-			to = strings.TrimSpace(to)
-			if !strings.EqualFold(to, "<valid-to@domain.tld>") {
-				writeLine(fmt.Sprintf("500 5.1.2 Invalid to: %s", to))
-				break
-			}
-			writeOK()
-		case strings.HasPrefix(data, "AUTH"):
-			if props.FailOnAuth {
-				writeLine("535 5.7.8 Error: authentication failed")
-				break
-			}
-			writeLine("235 2.7.0 Authentication successful")
-		case strings.EqualFold(data, "DATA"):
-			if props.FailOnDataInit {
-				writeLine("503 5.5.1 Error: fail on DATA init")
-				break
-			}
-			writeLine("354 End data with <CR><LF>.<CR><LF>")
-			for {
-				ddata, derr := reader.ReadString('\n')
-				if derr != nil {
-					t.Logf("failed to read data from connection: %s", derr)
-					break
-				}
-				ddata = strings.TrimSpace(ddata)
-				if ddata == "." {
-					if props.FailOnDataClose {
-						writeLine("500 5.0.0 Error during DATA transmission")
-						break
-					}
-					if props.FailTemp {
-						writeLine("451 4.3.0 Error: fail on DATA close")
-						break
-					}
-					writeLine("250 2.0.0 Ok: queued as 1234567890")
-					break
-				}
-				datastring += ddata + "\n"
-			}
-		case strings.EqualFold(data, "noop"):
-			if props.FailOnNoop {
-				writeLine("500 5.0.0 Error: fail on NOOP")
-				break
-			}
-			writeOK()
-		case strings.EqualFold(data, "vrfy"):
-			writeOK()
-		case strings.EqualFold(data, "rset"):
-			if props.FailOnReset {
-				writeLine("500 5.1.2 Error: reset failed")
-				break
-			}
-			writeOK()
-		case strings.EqualFold(data, "quit"):
-			if props.FailOnQuit {
-				writeLine("500 5.1.2 Error: quit failed")
-				break
-			}
-			writeLine("221 2.0.0 Bye")
-			return
-		case strings.EqualFold(data, "starttls"):
-			if props.FailOnSTARTTLS {
-				writeLine("500 5.1.2 Error: starttls failed")
-				break
-			}
-			keypair, err := tls.X509KeyPair(localhostCert, localhostKey)
-			if err != nil {
-				writeLine("500 5.1.2 Error: starttls failed - " + err.Error())
-				break
-			}
-			writeLine("220 Ready to start TLS")
-			tlsConfig := &tls.Config{Certificates: []tls.Certificate{keypair}}
-			connection = tls.Server(connection, tlsConfig)
-			props.IsTLS = true
-			handleTestServerConnection(connection, t, props)
-		default:
-			writeLine("500 5.5.2 Error: bad syntax")
-		}
-	}
-}